I have made a simple standard-dvd-video with a custom basic menu, using only free software on Ubuntu (Feisty) for pc i386.
Read it at Isotype
I have tried different gui-dvd-authoring software for Ubuntu, experimenting some difficulties for each one.
Actually (28 May 2007) the best choice, based on my personal experience, is Dvdman.
DeVeDe has a difficult interface for the medium-user.
Q Dvd Author gives more options, but crashes very often.