first of all: welcome to the forums!
Before sharing some ideas, let me confess a bias: I have the Nikon D40 with the 18-55mm kit-lens (not VR) and the 55-200mm VR). I take pictures similar to the types you mention (although not volleyball). I'm very happy with what I have and do not feel the differeces between the D40 and the D80 body is worth the price-difference. Others - inluding many here - have completely different priorities than I and value features, build etc. differently than I do.
I got some pictures posted in the various threads in these forums, but they are very likely not to reflect the full potential of the D40 I have - but at least you can see what another relative newcomer to D-SLR photography can do with it.
As far as the potential for image quality goes, they are as identical they can be without actually being the same camera.
The D80 has a sturdier build, composition grid (tic-tac-toe lines in your viewfinder, built-in flash command, built-in auto-focus motor and bracketing (three shots rapidly fired with slightly different exposure values, thus increasing your chance of getting one "just right").
The D60 has more built-in editing modes: star filters, sepia tones..things like that. It also has built-in time-lapse photography (take 1 shot every X seconds and bundle it all into a movie).
I'd strongly suggest that you check out Gordon's in-depth reviews of both to guide you further.
It's also a good idea to go to a shop and actually handle both - it often makes the choice a lot clearer.
The D60 comes with the 18-55mm VR lens - the newer sibling to the previous VR-less kit-lens that is largely identical.VR (Vibration Reduction: allows you to go hand-held for another 3-4 F-stops before needing a tripod to avoid camera-shake).
The price-difference (body alone) between the two is not very huge (but noticeable). Some would suggest that you should focus on the glass/lenses first, then the body. Camera bodies (with their assorted features) are evolving at a higher pace - mostly because of their tie-in with computer-tech). The glass however, doesn't evolve as fast.
In your position, you might also consider the Nikon D40 and D40x. They 90% identical to the new D60, but for a few features. They are noticeably cheaper.
If you can get a D40 (6MP) or D40x (10MP) body with the 18-55mm VR it will very likely be noticeably cheaper than the D60.
Such a set-up, compared to the D80, will have a noticeable price-difference that would then allow you to consider other items such as:
- another lens to supplement: sigma 10-20mm for the wide shots
I wish you good luck with your choice - they can all produce great shots for you.
When you've made your choice, I hope you will share some shots with us here in the forums