I've still never seen Undeclared, but I've heard good things about it. Although it's not actually a sequel to Freaks and Geeks, but it was Judd Apatow's follow-up show. There was an interview with Apatow where he was talking about why shows about college seem to never survive, and he was saying it's hard to do them truthfully on network tv, because the truth is that college kids are high, drunk, and having sex and no matter what you do, you're fudging it.