Brymon Airways (BA subsidiary) have, in the past, operated their Dash-8 300's (50 seats) with single cabin crew in "exceptional circumstances", last minute crew sickness/shortages etc and then only back to base with a reduced service at the discretion of the senior c/a concerned. It's pretty much frowned upon now as it's bloody hard work!! Other Dash-8 operators in the UK also fly regularly with 1 c/a as the legal requirement is 1 cabin crew member per 50 seats fitted. While at Jersey European we also operated the Fokker F27-500 (48 seats) with 1 senior c/a.
The First Officer normally reads the cabin brief before moving off stand, or a tape is played.