Which software is best for converting an AVI file and putting it on a DVD Rom?

I use Mac DVD Creator, but this is not freeware. If your wanting to burn AVI to DVD free then you will want to check out DVD Creator.

DVD Creator for Mac is a powerful Mac DVD burner designed for Mac OS users to edit and burn their videos files to DVDs. This Mac DVD creator can burn HD Video ( Burn MKV to DVD for Mac ). It supports almost all popular video formats including AVI, MOV, FLV, MPG, MP4, M4V, MPEG, DAT, VOB, 3GP, 3G2 and even HD videos such as TS, TP and TRP.This Mac DVD Creator is complete with highly customizable DVD menus. It also provides you with flexible functions to edit your videos such as cropping video, trimming video length, and setting video effects etc.

Source(s):
1.How To Convert AVI to DVD on Mac?
2.How to convet FLV to DVD, turn FLV into DVD, burn ...
3.How to Burn an iSO or .dmg file to DVD Disc?