For files --> DVD Movie
ConvertX is the the easiest, and just works.
The downside is, picture quality itself is really poor. It does however, convert most any format to DVD rather quickly with a fast 1 pass encode.
Cyberlink has a DVD authoring program (Power Director) as well that works well, although a bit pricey.
I just use Nero Vison & Recode for mine :-/
Sadly these are the only 2 I know of that do a decent job. Most of the free ones Ive tried end up having horrible quality in the end, or are lacking options.
(Like for making Home videos into DVDs)
For everything else, if DATA burning isnt included in your choosen app, IMGburn is really good for most all of your burning needs, and free.
Sorry couldnt be more help. As I say, most of the free ones Ive tried just looked horrible and I wouldnt recommend trying something to anyone I wouldnt use myself.
For DVD Authoring what features do you need really?
If your looking for something to create menues, title screens, cut & edit files to make a DVD will make a difference in whats available
as opposed to something that will simply convert a file to DVD format and burn it.