The D-Force non-slip/foam pads are great for beginner/intermediate players.
Omega series pads are probably the best hard dance pads on the market right now, they're the best you will find short of buying an arcade machine.
All the old adapters we used to have aren't sold/made anymore. If you've got any suggestions, please post about them!
FutureMax sells pads and adaptors for pretty much everything.