I am biased but not unreasonably so...
Best general folder (but not most compact) - Swift (aka Xootr in mast produced guise)
Best custom built (but not most compact) - Bike Friday
Best folder for commuting combo bike/bus/metro - Brompton or Merc
Best Value - Xootr or Downtube
2nd Best value - mid-range Dahons
If you are small the Brompton or Merc would be awesome.