pull-ups (palms facing away)
chin-ups (palms facing toward)
towel chins (drape a towel over the bar and do your pull-ups from the towel)
side-side pull-ups (pull up and touch your chin to your right hand, lower, pull-up and touch your chin to your left hand, lower = 1 rep)
sternum pull-up (from a dead hang, start as you would a regular pull-up but as you near the finish, lean back and pull the bar to below your nipples or lower-this is the most productive variation of the pull-up for size and strength imo)
commando pull-up (hands spaced about 4
inches apart and facing one another-pull up so the bar touches your right shoulder, lower, pull up so bar touches
left shoulder, lower = 1 rep
staggered-grip pull-ups (hands grab the bar shoulder-width apart with one palm facing towards you and the other facing away-now do your pulls.switch hand position each set so you get an even amount of work with both grips)
There are a few more variations but these should give you a fair amount of variety for now.