Reported spam aside, there are a number of free or low-cost ways to do this. One of my favourites is the free MPEG Streamclip, which despite the name converts AVI files into a variety of other formats.
Another great one is the late lamented Visualhub, sadly no longer available for download, but replaced by a small army of new apps using their source code, such as Video Monkey, Redux Encoder and FilmRedux (all free). There's also Evom and iVideo Converter (small fees IIRC), the venerable ffmpegX, and VH still works in Snow Leopard if you can find it.
On the pay side, Toast (either v. 9 or 10) makes the whole process incredibly easy: drop in file, put blank DVD in burner, do something else for a while, done.