.... hmmm, normally I wouldn't touch that on a forum with a 10 foot pole but since we're all honest blokes here at Datsun 1200.....
An easy way,
Get yourself a copy of DVD shrink
Clicky, not sure if it's the latest version thoughRun the program, then:
*Open Disc... wait for it to analyse the disc
*Click re-author (top right)
*Drag the chapter you want to take a clip from from the right field into the left
*right click that chapter (on the left) and click "set start/end frames"
*choose the start and end of the clip you want to take, click okay
*Then click the backup! button up the top of the main window.
This will rip it to your hd wherever you tell it to, then you need to convert it to whatever format you want, lots of free programs for that too.
I did this to make a compliation of the best car chases from all the dvds I own, quite enjoyable over a beer or 10.
There are probably far easier ways to do it but that's what's always worked for me, hope it helps.