Bah, I've had all this written up for you for forever. Here you go.
Get this case:
http://www.newegg.com/app/ViewProduc...ion=11-129-120
Here's a good motherboard:
http://www.newegg.com/app/ViewProduc...ion=13-131-429
If you want built-in FireWire, you can get this motherboard instead:
http://www.newegg.com/app/ViewProduc...ion=13-131-421
The second one is technically a better motherboard and isn't much more expensive, but they're both very good.
Here's your processor - 2.4GHz
http://www.newegg.com/app/ViewProduc...ion=19-116-139
I really recommend 512MB of RAM instead of 256. Here's a great stick from Crucial:
http://www.newegg.com/app/ViewProduc...ion=20-145-059
All of that's available at NewEgg.com. It might be a little more than you wanted to pay, but there's nothing bad about the parts I just recommended.