Yes there are. One company that sells them is Smarthome, they have a few versions, ranging in price from $50 or less to several hundred dollars. You can also go to Radio Shack and buy a distribution amplifier for $40 or so. I bought one of these, which does a very fine job of converting S-Video to Composite or Vice Versa. The amp I use has one input and four outputs. Don't remember the model number, sorry.
Niels.
Niels.