How about using an Arduino to control it?
Ahh.. good. Another brand/source for this kind of stuff. These ones look a little less turn-key than some of the others, but in the same ballpark for price.
Thanks!
The Arduino is all open hardware/open source, so of course it'll be a little rough around the edges

There are a lot of people using them for little projects just because it is so easy to work with.
Also since you're looking at just a USB->Serial with some GPIO pins, take a look at this
http://www.gridconnect.com/xportdirect.html It is a Ethernet to Serial interface also with some GPIO pins.
I'm using one of those hooked into the Arduino I've got so it can talk to the network directly without needing a computer.