Don't forget your OS. Most offer OEM software with a purchase for around $100. Also,
www.newegg.com has some good deals on HDD's like
this one. Double the storage for $25 more.
Don't forget a dvd-rom/burner. I have had good luck with
Benq on the last 2 I've built but alot of other people like the
NEC. You can't go wrong with either but the couple extra $ for a burner is worth it.
You also might want to throw in a floppy drive like
this. Can't hurt for <$10. Very helpful if you need to make a boot disk.
I assume you are getting the 1GB Ram stick to upgrade later. If not maybe stick w/ 2x512mb for dual channel.
I have built a couple but mine were mainly for gaming. Hope this helps.