This month in circuit cellar 02/2005 issue 174
This one is a Avr that does USB and I think bit bangs out RS-232, they used it to control a remote control car. if you need to do something via USB this looks easy.
ftp://ftp.circuitcellaronline.com/pub/Circuit_Cellar/2005/174/Stadelman_MacEvoy174.zip
This one seems to be something that runs a wifi PC card. No schematic but what is in the Mag is not very much.
ftp://ftp.circuitcellaronline.com/pub/Circuit_Cellar/2005/174/Eady174.zip