Hulu put up the whole first 12 over the winter hiatus, but of course, that doesn't help now! (I wish all shows kept full seasons available).

However, I know you can watch them all here:

http://ch131.com/communityseason1.htm

The site only has one ad on top of the video that can be closed, and I haven't had any issues with popups or malware.

BTW, I loved it from the pilot on... but not everyone did. Most people agree that the show found its stride around episode 7. The highlights for most people are eps 4, 7, 8, 9, 10, 12, 13 and 15.