I wrote an article right here on eham.net a couple of years ago.http://www.eham.net/articles/8192
As for the people claming you need an extra chip and the added complexity, my set up is still working just fine after two years!
As for the USB board, check www.mouser.com
as the price has dropped and the latest boards are better. Just download the free datasheet for all the information you need to build one. There even easier than the old $10 rs-232 to TTL interface projects!