Depends what you want to do with them. If you want to play them on your/others domestic DVD players you need to find out what format your domestic player is. Most are -r a few are +r and there are a lot of multiformat players out there. My domestic player is multi format (not multi-region though) so I can use any DVD disk. Once you have sorted that bit out check out this previous thread for where to buy.
I find that +r DVDs are slighty dearer than -r.