What are you planning on doing with this build? Do you have a preference between Intel/AMD? What type of RAM do you have? Providing more information will make it a lot easier to provide meaningful advice.
Im wanting to make a gaming pc, but the i7 is over my budget. I have 4g ddr3 ram. I was leaning toward the phenom x3 720, since its am3 and can use the ram and it looks affordable. As far as the gaming, only wanting to use a single video card, no sli or anything..