Yes! Thank you for the info about the Mouser boards, I didn't know they had stuff like that.
Upon further research, I also found this vendor with the serial boards:
http://store.nkcelectronics.com/freeduino-serial-v20-p20.html
I like the version from Mouser in that it uses transistors for the serial-to-TTL converision.
Thanks to all for the help.