Labar had the best suggestion, but I'm gonna go on a limb and tweak it a bit.
You could get a motherboard that'll last longer in case you decide to upgrade in the long run, and it'll also over-clock really nicely.
www.mwave.com was used for my bundle suggestion:
Intel Pentium D 820 Retail $95.88
Gigabyte 945P S3 $81.62
Kingston 1GB DDR2 533 $66.25
Total: $243.75
The bundle ends up being cheaper than Labar's suggestion, is a little less powerful, but you get a much more concrete motherboard base and you can easily over-clock this processor to 3.5+ gigahertz.
The thing is, you get left with a little under $100 for a video-card.
If you want, you can buy my 7600GT off me. I'm selling it for $85 shipped. It's the BFG OC'ed version, I've only had it for about a month now and haven't over-clocked it. You get a pretty much brand new 7600GT without having to wait for a rebate and I guarantee it'll run good for you.
If you can't afford that, you can either bump up your budget to get the 7600GT new for your build, or you can get maybe an X800GTO2 if you can find one, or a 6600GT.