Do you have the only RS232 output on your computer connected to some AV equipment like your TV? And you want play around? A RS232 expander is easyly made. You could even automate the switch to control both a TV and an amp.
The serial header of a Linksys WRT54G provides TTL voltage levels. However for debug purposes, it could be handy to connect the automation network directly to a PC. That is why we need a RS232-TTL converter. Mine is based on the MAX233 with the possiblity of handshaking when needed, just place the jumpers accordingly.