There are some HDMI to component adapters. I think I've even seen them in stores like Target under the RCA brand. They were around $30-$40 if I remember. Depending on the adapter, you may even be able to get HD with it, and not limited to SD.
That said, some basic TV's are getting so cheap it may be better to just replace the TV. Even a cheap TV may have a better picture than an older, pre-HDMI TV.