Quite a few people on the forum have D3000's, and you'll find a few threads in the Camera Corner discussing it and other Nikon DSLRs. For example,
Name your camera - you'll see a number of D3000 owners on this thread
Got a new lens, have some questions - about using a 50mm lens on the D3000
Fixed length lenses - about fixed (non-zoom) lenses and flash
I DID IT! - from and to a D5000 user, but the cameras are pretty similar
Dreaming about a new camera - discussing various cameras, including the D3000
Showing off some spring pix - care of Sasha, the D3000
Nikon D5000 - starts with the D5000, but also discusses the D3000
Nikon D3000 or Canon EOS1000D?
Another Camera Thread
I have a D300 myself, which is at the other end of the Nikon consumer DSLR spectrum, just below the professional D700/D3s/D3x level. I'm a big fan of Nikon, but I should say that you tend to stick with whatever line you start with - Canons are equal in quality, and Canon users are typically as happy with their cameras as Nikon users are with theirs.
The D3000 was a good entry level DSLR (it has since been replaced by the D3100). It's small and light and capable of taking very good pictures. One of the good things about getting into an entry-level DSLR from Nikon (or Canon, for that matter) is that any lens you buy for the D3000 will work with any of the more advanced Nikon DSLRs, if you later decide to upgrade. The D3000 has all of the basic features you'd expect, plus the "point-and-shoot" automatic modes which you can lean on until you become more comfortable with photographic techniques (interestingly, the more expensive and capable a camera is, the fewer of these modes there will be - my D300 has no automatic scene modes at all, just Program, Shutter and Aperture Priority, and Manual).
Ken Rockwell has
a review of the D3000 on his website which is well worth reading.
The 18-55mm VR lens that Craiglist ad is selling is the basic "Kit" lens most D3000s were sold with. It is a decent zoom, running from wide-angle to short telephoto range. If the "18-55" part doesn't mean anything, see the thread
What are those numbers... which explains lens focal length. The "VR" (Vibration Reduction) feature is nice - it allows you to take pictures in lower light by compensating for camera shake. I have several VR lenses, and I like the feature (just be sure to turn it off if you're using a tripod).
The one drawback with the D3000 (and D3100, 5000, D40 and D60) is that while any lens which will fully work with these cameras will work with the advanced Nikon DSLRs, the reverse is not true. The D3000 and its relatives require lenses with built-in focusing motors (the AI-S series, for Nikon brand lenses). Many of Nikon's better lenses, and many lenses from second-tier lens manufacturers like Tokina, Tamron, Sigma, etc., do not have these motors and can only autofocus with cameras which have motors in the body. That doesn't mean you can't use the lenses with the D3000, but you can't use the autofocus capability so you'd have to focus manually. Since you're starting from scratch you can avoid the problem by being careful what lenses you buy, but you should know that it will limit your choice somewhat.
The D3000 also can't use any of the much-older manual Nikon lenses (those without the built-in CPU chip), but that's true of all Nikon electronic cameras (DSLR and film) below the D300 "pro-sumer" level. If you don't have any old Nikon lenses, that's not really much of an issue.
