MTT's are alive & well. SNG's (Single table or Multitable sng's like the old 45's, 27mans, 180's) are pretty much ancient history. Any sng's you'll find will be Turbo or Hyper Turbo. You won't find 'regular' speed SNG's these days.
A.C.R. (&/or BlackChipPoker on Winning Network) is probably the busiest site you can play on. I hear good things about Global Poker too. (but I've never played on there myself).
Downlaod the ACR site and have a look at it for yourself.
All of the sites have a 'RUSH' style cash game (Stars > "Zoom", PP is FastForward, 888Poker is 'SNAP', ACR is 'Blitz', GGPoker is 'Rush & Cash', TitanPoker is 'SPEED')