A modern day 'Open all Hours'?... pharmacy hasn't been tried yet?
Setting Needed! Page 2
I read someone once say that sitcoms need to throw together contrasting characters into a confined setting that none of them can escape from (Porrige, Red Dwarf, etc), so how about a series where the whole thing takes place in a cramped commuter train on the way to and from work? That would be a challenge to any scriptwriter! 
How about a crack den in a squat? You could have various rooms in the house with various types coming and going?