If you want amd, get something along the lines of a athlon x2 5000+ (get a black edition if you want to overclock) and pick a motherboard from here: http://www.anandtech.com/guides/showdoc.aspx?i=3157&p=3 (or any good list of amd motherboards)
If you want intel, get a processor from the e2XX0, e4X00 or e7X00 series (depends on what fits in the budget) and pick a motherboard that fits in the budget with it. http://www.anandtech.com/guides/showdoc.aspx?i=3157&p=4






