There was a rumour of a sitcom about a pub quiz team which would've been original, if a bit one dimensional. Got me thinking about other original(ish) ideas.
There are definitely possibilities in a sitcom about a crazy golf course.
Kerry Katona: My Life Story aka 1001 ways to get on the front page of Chat!.
The Pakistani national football team on tour in Scotland.
The mobile burger stand or Ice cream van.
The chippy (or chipper, if you live in Manchester).
Come on then, your starter for 10.
Sexual rehablitation clinic.
I've never seen a sitcom set on an oil rig in the north sea.
Lice in a prostitutes vagina.
I once thought about writing a sitcom about patients who had been amputated from the waist down, but I didn't think it had legs.
Never seen a sitcom about an ex-brickie turned writer?
Quote: Rick Skelton @ January 11, 2008, 3:14 PMIce cream van.
'The Ice-Cream Man Cometh' from That Peter Kay Thing, was really good. I would've loved to have seen more episodes of that. 
Paedophile ring.
Quote: Charles E. Lawley @ January 11, 2008, 3:27 PMPaedophile ring.
Is that the name of an organisation or an act?
My uncle would have definitely watched that.
Unbaptised babies in purgatory.
180' - The sitcom that looks at the glam world of international darts
Pipes - New ITV sitcom based on a Colonic Irrigation company in Penzance
Solstice - A hysterically look into the life of a group of druids
Quote: ContainsNuts @ January 11, 2008, 3:20 PMI once thought about writing a sitcom about patients who had been amputated from the waist down, but I didn't think it had legs.
Finding you're married to your seperated-at-birth twin sister...
My vagina sweating furiously from hours of action!
Chaaaarellyyyyyyy! 
(*says it in a very "Ooohhhhhh!" 50s American sitcom manner*)