For saving data/video and playing it back on the same machine:
DVD-RAM
(Newer DVD-RAM drives may be readable on other devices, but YMMV)
For Authoring
DVD Forum approved video DVDs that have the highest chance
of compatibility with consumer DVD players:
DVD-RW
For the best general data storage options, along with a high probability of
compatibility with consumer DVD players when doing video authoring:
DVD+RW
There are various (and somewhat confusing)
guides on the net that explain each standard.
But, IMHO (and for my personal usage pattern) DVD+RW currently offers the best
combination of support for DVD-Video, DVD-Data storage, and using the drive to also
burn CD-R, and CD-RW. The downside is there is not yet a straight DVD-Recordable
standard (DVD+R) for these drives. (Supposed to come out sometime next year).