Very basics - any Crank Brothers or Park Tool that has 4,5,6 and a screwdriver.

Boy Scout Material - My favorite is the "Rescue Tool" from Park, it has everything you need (including built in tire levers) but also separates in to two halves, so you can leave the half with all the true EXTRA's and chain tool at home, if you aren't going far.

http://www.parktool.com/products/det...=11&item=MTB-3