One of the things I gave my wife for Christmas was the complete set of Blackadder on 4 DVDs (all the episodes in all 4 series, but none of the specials). We're onto the second series now (actually I think tonight we'll see the last episode in Blackadder II), and they are so funny they make me laugh out loud (I've seen them all before - but they're not the type of thing you get sick of seeing again). I think Blackadder is possibly the funniest TV series ever made.
The first series was odd though. It's hard to put a finger on exactly why the first series wasn't funny. It has different writers: Richard Curtis and Rowan Atkinson, whereas later series were all written by Richard Curtis and Ben Elton. It focuses a lot more on different characters, whereas later episodes focus more on Blackadder himself. And Blackadder isn't as smarmy in the first series. Still worth watching though.