Most of the main mulitimedia players on linux can play dvd images or directories from HDD. All you have to do is use the correct launch syntax.
mplayer dvd://1 -dvd-device /path/to/dvdimage
(The '1' being the first title on the disk)
These will work both on .iso images and on any directory containing a VIDEO_TS folder. Other players probably have similar commands. Check the player man pages for info.
Whether to go with an .iso image or to rip the files to a directory is really up to you. A directory full of image files is a bit easier to manage, but a copied dvd structure can be more easily accessed (you can play the .vob files directly, for example, instead of the whole disk).
Of course, you do realize that the average dvd is about 8-9 GiB in size, don't you? If you want to save yourself some room, at the expense of some quality, you can use a program like k9copy or dvdrip to shrink the image down to a smaller size as you rip it. Or you could always simply rip the titles to compressed video like ogg theora or .mp4 instead.
*Here's a useful trick for you. The xine command especially requires the full path to the device and won't accept relative paths like '~/myvideo'. But you can easily insert the necessary parts by simply using '$HOME' or '$PWD' (for the current working directory) instead:
Last edited by David the H.; 12-19-2007 at 05:39 AM.