Layout is good, very clean and organized. Color scheme matches well, but I don't like the shades of green much (I'm not really a big green fan, anyway). The way everything is presented is very coherent, and its easy to understand where everything is and why it is there.
Only real quibble I have is that the background is.. well, not in my taste You might be better off going with a simple diagonal line background instead of that fancy one.
Also, I will say that artistically the site isn't that appealing - the bevel on the header logo looks cheesy (most bevels do), and the font for the logo is way too pixelated, and needs some anti-aliasing. Most people aren't going to care that much, though.
As a side note, something I recently picked up as far as useability goes - Put the content that you want people to read first near the top of the .html file code wise, if you can (css makes this a lot easier, thanks to positioning ). This is good for TTS readers for the blind, and also good for browsers such as Links/Lynx, which are text based and ignore stylesheets. Not a necessity, but it is a good practice to follow (which I'm guilty of not following quite often ).
Otherwise, I think its a good site. Nice work