I use TMPGEnc 2.5 to convert my video clips (Divx, Xvid, WMV, etc etc) to a format accepted for DVD video (MPEG or MPEG2). Then once my clips are converted I use TMPGEnc DVD Author to create my custom menu's insert the clips and produce the file structure needed for a DVD (AUDIO_TS, VIDEO_TS, IFO, BUP etc etc).
This program also has a burning tool built in which I use to burn all my DVD movies I create. As Warez mentioned though Nero does this as well. I use DVD Shrink when I need to backup any of my scratched DVD's it works great.
I also played with this program called Super DVD Creator 8.5 which allowed me to directly insert non-DVD supported formats (divx, xvid, wmv etc) into the creation software and burn the disc, but I didnt have the cool menu creation options as the above program.