Some burner apps will do the conversion for you. eg: Roxio or the latest Nero versions. If you have an avi or mpeg1 file, they will do the necessary conversion before they begin the actual burning process.
As for other converters, well you can check these places out: 1.
http://www.videohelp.com/
2.
http://www.videohelp.com/tools 3.
http://forum.dvd-guides.com/