Whats the name of your printer? If its a canon or epson you could probably get some cheap generic ink on ebay. Otherwise Fry's has good prices on name brand ink.
http://www.123inkjets.com man, after using them I'll never buy ink at retail again. Free shipping and even some free (albeit not that great) software bonuses. There are some great bundle deals too. A black and color cartridge that works great on my printer cost me about $15 shipped. You may wanna try out http://www.4inkjets.com too, I've heard good things about them as well.