I think my fave is South Park at the minute. That whole 200th episode malarkey (has that even been officially released over here? I've only seen it through iTunes or whatever it gets called) was brilliant.
Over the last few years I have also liked Outnumbered (put it on by mistake but it was a right laugh!), Blackadder (had plenty of laughs playing George in a College rendition of Goodbyeee!), Open All Hours (especially the whole stutter thing; it gets quite funny trying to impersonate Ronnie and then stuttering myself...!) and, although not as much as previously, The Simpsons. I also like select episodes of Family Guy (Blue Harvest was a good one; haven't seen the others yet), and also some sketches in Monty Python. I didn't like Life of Brian much though. I would also give good mentions to the two great quiz-comedies of the Beeb, Have I Got News For You and QI.
I can't always understand British humour though. By autistic standards my sense of humour is quite good but it's still not all that. Fawlty Towers is hit hard by this.
Another one I would suggest, although not exactly a comedy, is Corrie. Some of the traditional Corrie charm is comedy-based; I guess Norris "Mole" [anyone seen the actual Norris Mole blog thing?] is a good example of this.
And lastly, does Top Gear count?
), Porridge, Fawlty Towers etc, and Family Guy and The Inbetweeners from the modern era, but I need more options.