Sigh - i've just written a column for a trade mag about this. The law needs a rethink right now: technically it's illegal to make copies of DVDs, even ones you already own, as they're copyright protected - meaning you're in breach of copyright law even trying to copy them.
Whereas with music it's considered 'fair use' to make back-up copies of discs you own (though, as discussed here recently, also still technically illegal), movies remain a far thornier subject.
Far be in from me, therefore, to suggest you type elements of your question - such as DVD, iPod and conversion software - into Google to see the opinions of others on the matter...