Depends on where I'm going really.
2-3 sticks depending on length of session
extra change of clothes (shirt/shoes/socks/boxers)
Two extra sets of clothing
3+ Bottles of water
I used to travel with a lot more stuff, but I really only take what I need now.
http://tt.tennis-warehouse.com/showthread.php?t=496820 - Help get BruceD a new tennis wheelchair!