The Linux Video and DVD Project has made great headway since its start last February. Also provided on the site are links to various documents discussing DVD chipset specifications. The Linux Video and DVD Project is avidly seeking help from the opensource community for development. See also DVD-Playing-HOWTO.
Universal Disk Format (UDF) Driver: "UDF is a newer CDROM filesystem standard that's required for DVD roms. It's meant to be a replacement for the ISO9660 filesystem used on today's CDROMs, but the immediate impact for most will be DVD. DVD multimedia cdroms use the UDF filesystem to contain MPEG audio and video streams. To access DVD cdroms you would need a DVD cdrom drive, the kernel driver for the cdrom drive, some kind of MPEG video support, and a UDF filesystem driver (like this one). Some DVD cdroms may contain both UDF filesystems and ISO9660 filesystems. In that case, you could get by without UDF support."