You should be able to get the AMD Phenom II X4 965 Black Edition 3.4GHz for exactly $200 USD. It's a lightning fast quad core, and it's a black edition which means if you were ever to overclock it you don't need to have any previous knowledge as you can just up the multiplier - dead simple.
A good motherboard for this depends on budget and needs.
Do you need multiple graphics cards, and if so are you using NVIDIA or ATI?
Do you need it to be a set size (MATX, ATX or EATX)?
What RAM do you plan on using? DDR2, DDR3.. and what speeds?
If you really aren't going to overclock, because you're scared or you just don't know, then I say go with the Intel Core i5-2500 which is currently $209. Of course, getting a motherboard for it is exactly the problem right now so you will have to wait for a few weeks unless your o.k with your SATA ports possibly dying. If you use certain kinds of heavily threaded workloads, like certain rendering programs, then you may want to look at the AMD 1090T instead. As for the motherboard are you interested in SLI or Crossfire? What are you going to be using it for?