Both the D90 & D5000 offer movies at 720p. But note that AUTOFOCUS is NOT available when shooting a movie on both! The 5000 has the tilting screen.
The D90 is a great camera, but frankly might be overwhelming if you are just getting into it. There are a lot of features it offer that you may never even use.
I would recommend starting with a D60 off Craigslist and see how much you really want to get into the hobby. Great pictures can be taken with any camera, its just the "toys" that go along with them. The Megapixels are roughly the same (10 v 12) so you can still have a good sized image to crop.
Honestly, the best money is spent buying great glass (lenses). They make the picture more than the camera itself.
I had a D40 for years and really loved it, once I got the lenses I wanted I moved up to the D90, which I find to be a great camera as well.
As far as Canon/Nikon, both are good companies, but I say buy what your friends have, that way you can borrow their lenses if you need to. And speaking of lenses, these things can get crazy expensive, but you can rent them cheap and try them out. I used rentglass.com and found it was a great way to find out which lenses I wanted to blow my money on.
If you would like more info, PM me since I have owned both! Check out my flickr
www.flickr.com/chriswhitpan and you will see some possibilities with both cameras.