I know it's the age of blu-ray and HD-DVD, but here is a list of a *lot* of questions around DVD discs. It gives a lot of thorough information about the discs themselves, where can you buy such discs, players that support them and pay attention to the differences of the 5 types (DVD-R, DVD-RW, DVD+R, DVD+RW, and DVD-RAM). On the other hand, Webopedia's is the alternative guide I'd recommend.
Have fun reading!
"Learning is experience. Everything else is just information." -- Albert Einstein