What other dry foods can mix my rabbits pellet food with?

i feed him unlimmited hay rabbit pellets, and alfalfa cubes and i'm going to start feeding him the vegetables my rabbit care book recommends. i was wondering what other dry foods can i mix With my rabbits pellet food? is rice or oatmeal o.k.? cooked or uncooked? and are there any dry beans he could eat?.....ummmm and what about cheerios? thanks alot :)