This is irrelevant to anyone who's not in the U.S., since Hulu.com still blocks access to un-American computers, but they seem to have added some additional episodes recently. Most shows still don't have their full runs available and many are still stuck at one season (like WKRP which only has the one season as chopped up and wrecked for DVD release), but there are some season 3 and 4 episodes of Barney Miller, and those awful episodes of Archie Bunker's Place where they announced that Mike had abandoned Gloria just so they could spin her off, in addition to the stuff that was already on there, like the first season of Lou Grant. In the guilty-pleasure category they have the third season of Weird Science (which has most of the best episodes but will probably not be on DVD) and some even more obscure '90s USA network shows like Campus Cops.
There are ways to disguise your ISP and get into Hulu even if you're not in the U.S., but I haven't figured out how to do it yet. So for the moment, Hulu is for you-lu if you're in Maine or Honolulu, but you're out of luck if you're a Canuck or a Zulu.