You might want to check out
Robot Combat. However, the IFI Victors are arguably the best speed controllers on the market. (As long as you aren't running insane current through them) You might be able to find a cheaper one that would serve the purpose, but old 883s are probably the best choice. Controllers... that's more personal preference, the Vex ones are nice though... You could try making your own speed controller out of a rheostat or high current potentiometer and a servo, but that would make a lot of heat and waste power.