A quick video to show you some useful track mode keyboard shortcuts in protools. These work in ProTools 8.0 and above, I have not tried them in 7.

Record arm a track (your cursor must be placed on that track): Press Shift + R
Place track into input mode: Shift + I
Place track into mute: Shift + M
Place track into solo: Shift + S

ProTools: Record arm a track from the keyboard from Nick Daley on Vimeo.