The D5000 is a weird slotting on Nikon's part. I almost think it's Nikon's little jar of peanut butter meant to move you up to the larger jar by comparison, seeing the larger jar as more bang for your buck.
If you can stretch a bit more, the D90 is far more camera than the D5000. Significant advantages of the D90 to the D5000 include:
1. Larger LCD with twice the resolution (twice the sharpness and detail). Same screen as on the D300, D700, D3 and D3x.
2. D90 has a top LCD. I use this and appreciate it much more than adjusting settings via the rear LCD. Also uses less battery than turning the rear LCD on all the time.
3. D90 has an autofocus motor for AF lenses without an internal motor such as the Nikkor 50mm 1.8 and the Tokina 11-16mm 2.8, both excellent lenses cheaper than their internal focusing Nikkor counterparts. This alone is justification enough to get the D90 over the D5000 if you want one of these lenses as the price difference in lens will make up the price difference in cameras.
4. D90 has nearly twice as many buttons/switches as the D5000 for easier/quicker camera control.
5. D90 has a more rugged "feel" to me. The D5000 follows the D40's form, both of which are very good, but the D90 is definitely a step up.
6. D90 has a noticeably brighter and larger viewfinder. It uses a pentaprism like the D300 and up, not the pentamirror of the other models.
7. The D90 can wirelessly control external flashes. The D5000 and below do not have this capability built-in.
I'm sure there's something I'm leaving out, but that should give you an idea. The D90 is only slightly larger and heavier than the D5000....maybe 15% more, but feels very well weighted and balanced. It doesn't have the swivel screen of the D5000 which I find gimmicky anyway and would never use. Both should shoot the same quality video.
EDIT: I moved from a D40 to D90 recently. I shoot professionally and am in a gallery in Ashland, Oregon. If your budget is really tight, think about a D40. It is a perfectly capable camera. It is an older model than the D5000 and D90 and doesnt have all the bells and whistles, but I've been using mine for 2 years with happy results...and if anyone's interested, I will be eBaying my D40 with extra battery and SB-400 external flash soon. Contact me off list if you are interested before I put it up for auction.
All the best,
Jesse Widener
Art and Structure