As longtime readers know, one of my spare-time occupations is amateur astronomy. I often get asked by friends and colleagues for telescope recommendations, so (just as I did last year), I'd like to provide some, along with some background on the whole topic..
The key thing to remember with a telescope is that other things being equal, aperture wins. More aperture means that you will be able to see more objects and more details. It's only fair to note that not all amateur astronomers agree with this, or about which kind of scope is best. As you'll see, larger apertures involve some compromises. And keep in mind that while a bigger scope can show you more, the best telescope is the one that you'll actually haul out and use. Overbuying has not been my problem, dang it all, but it has been known to happen. These days, eight-inch reflectors are a good solid entry point, but smaller ones will be cheaper (and perhaps worth it to see if this is something you really want to get into).
There, I've mentioned reflectors. Those are one of the three main kinds of scopes to consider: the other two are refractors, and folded-path. The refractors are the classic lens-in-the-front types. They can provide very nice views, especially of the planets and other brighter objects, and many planetary observers swear by them. But per inch of aperture, they're the most expensive, especially since for good views you have to spring for high-end optics to keep from having rainbow fringes around everything. I can't recommend a refractor for a first scope, for these reasons. A cheap one is not going to be a good one. That's especially true since a lot of the refractors you see for sale out there are nearly worthless - a casual buyer would be appalled at the price tag for a decent one. (Scroll down on that link to see what I mean). No large refractors have been built for astronomical research for nearly a hundred years.
That said, refractors have very, very devoted fans. If your vision is discerning enough, you'll enjoy the views through a really good one more than through any other kind of scope. But if you're just starting out, your vision is almost certainly not good enough yet (see below), so I continue to steer people away at first.
The next type, Reflectors are all variations on Isaac Newton's design: open tube at the top, mirror at the bottom, and an angled secondary mirror back near the top to reflect the light out to the eyepiece in the side. All modern large-aperture research telescopes are some variety of reflector. They provide the most aperture per dollar, especially with a simple Dobsonian mount (more on mounts below). One disadvantage compared to the other two types is that reflectors have to be aligned (collimated) when you first get them (and every so often afterwards) to make sure the mirrors are all working together. A badly collimated reflector will provide ugly views indeed, but it's at least easy to fix. It's also true that if the primary mirror is of poor quality, you're also in trouble, but the average these days is actually quite good, and this really isn't much of a problem any more.
Finally, the folded-path (catadioptric) types (Schmidt-Cassegrain and Maksutov designs, mostly) are a hybrid. They have mirror in the back, but also a thin corrector plate covering the front, which also has a small secondary mirror in the middle of it. The light path ends up coming out the back of the tube, through a hole in the primary mirror. Like refractors, these basically never have to be aligned. They're more expensive per aperture unit than reflectors, but a lot less than refractors. Their views are pretty good, although purists argue about how they compare to a reflector of equal size. (Refractor owners would probably win that argument, but they have to drop out at about the five or six-inch mark, when the other two telescope designs are just getting started). These designs are also compact (all that light folding), which makes the more portable and easier to mount.
And that brings up the next topic: what you do mount one of these fine optical tubes on, so you can use them to actually look at things? An equatorial or a fork mount will let you follow the motion of the objects in the sky easily, especially with a motor drive - the Earth's rotation is always sweeping things out of your view, otherwise. A decent mount of this kind will definitely add to your costs, though. The "Dobsonian" mount is a favorite of reflector owners, since it's quite simple and allows you to put more of your money into the optics. You do have to manually grab the telescope tube and move it, though, which takes some practice (and often some home-brew messing around with the mount). Some people don't mind this, others are driven nuts by it. You can put a motorized platform under a Dobsonian (my own setup) to motor-drive it, which some consider the best of both worlds. This is, though, suitable only for visual observing; a platform is almost never good enough for real astrophotography (see below for more).
On the topic of motorized telescope mounts, I should say something about "Go-to" models. These are not only motorized to track objects, they will slew the scope around to find them from a database or by manual entry. I'm very much of two minds on these. For an experienced observer, an astrophotographer, or a researcher, they can be an indispensable tool to spend more time observing and less time hunting around. For a total beginner, they can ease a lot of frustration when first learning the sky. But at the same time, they also can keep you from learning the sky at all, and they can very definitely encourage hopping around too quickly from one object to another. If you do that, you can "see" all sorts of stuff in one evening, while at the same time hardly seeing anything at all.
That's because visual observing is all about training yourself to see things. One thing every new telescope owner should know is that Very Little Ever Looks Like the Photographs. Especially since the photos are long exposures on wildly sensitive CCD chips, usually through big instruments, and under excellent conditions. Through the eyepiece, I am very sad to report, nebulae are not tapestries of red, pink, green, and purple: they range from greenish grey to bluish grey. And although with practice you'll pick up really surprising and beautiful amounts of detail in deep-sky objects, at first, everything can look like a blob. Or a smear. Or not appear to even be there at all, even when a practiced observer can see it right smack in the center of the eyepiece field. I really enjoy seeing these things with my own eyes, and trying to find out just how much detail I can pick out and how faint I can go, but it's not for everyone. This is one of the single biggest things that needs to be emphasize to anyone planning to buy a telescope. Even the planets need practice: you'd be surprised how small Saturn is in a budget eyepiece, although it's striking at almost any magnification. If conditions are bad, Mars and Jupiter can look like they're at the bottom of a pot of boiling water. And you need time and patience to see all the details there are to see on them.
Now, photography is another story. Astrophotography is an expensive word, although thanks to webcams and the like, getting into it is not quite as bad as it used to be. But for most purposes, you'll need one of those motorized mounts that'll track objects across the sky. That's very convenient for visual observing, too, naturally, but a really good one for long-exposure photography can cost more than the telescope itself! I'm not an astrophotographer myself, so I won't go into great detail, but if you want to try this part of the hobby, prepare to think about the telescope mount as much as you think about the optics. Imaging equipment ranges from simple webcams all the way up to wonderful stuff that easily costs as much as a new car, or perhaps a small house. And you'll also need to be prepared to learn a lot about digital post-processing. That's another thing that all those great astrophotos have in common: someone spent a lot of time working on them, after they spent a lot of time gathering the data in the first place.
So, what to buy? I've scattered some Amazon links in the above to representative scopes. In general, Meade and Celestron are the two brands you'll see the most, and if you stay away from their cheap refractors, you should be fine. And Orion also sells good stuff of their own brand, (on Amazon and from their own site). (Again, I'd stay away from inexpensive refractors there, too). Other good sources are Astronomics and Anacortes.
There are a lot of excellent resources for specific opinions on different models, and on telescopes in general, at Scopereviews. Cloudy Nights is also a huge resource, full of message boards on every amateur astronomy topic you can think of (and classified ads for used equipment as well). Rod Mollise has a lot of good stuff, if you can handle his folksy dialect style. For the truly hard-core visual observer, Alvin Huey at Faint Fuzzies is a great source for downloadable observing guides (many of them free). I use them, although there are plenty of objects in them that are outside my range (I use an 11-inch Dobsonian reflector). He has observing guides for sale, too, but every single thing in every one of them is outside my observing range. Dang it all. And I can recommend the free software Cartes du Ciel (Sky Charts) for printing out charts of your own.