Hi,
I'd second the earlier post recommending the toppeakRoad morph - i'd never leave home without it (well when I'm cycling anyway). Personally I take with me 2 spare tubes, punc repair outfit, tyre levers and multitool - but it really depends on how far away from home you go - I commute some 36Km away and needed everything I 've taken with me at one time or other!
Happy cycling!
