M-Audio does some nice desktop active speakers as well and actually I was thinking about getting M-Audios myself. Unfortunately as praised as the AV40s are they are just way too big for my desk. M-Audio does have AV30 as well which are smaller and good as well (although not as good as the AV40) but they are still too big. Don't even consider AV20.
I agree with the comments about Bose. They make stylish speakers that are decent but, as was mentioned, they are way overpriced. Those Harman/Kardon speakers are very popular among mac-people but for my taste they are just too "alien". For me the Audioengine A2s are the best option: incredible sound (even bass although some opt for an extra subwoofer), surprisingly low price considering the performance and they match the new iMac perfectly. And they are surprisingly small as well.