Dual layer, or single layer? I only do dual layer any more as having a 104" screen, you start to notice flaws in some regular DVDs, so backing them up and squishing them to a single layer just made it worse (again, only on some, mainly older, titles)...
For dual layer, I am a BIG Verbatim fan. I have tried all sorts of discount brands - Memorex, The Best Buy brand (don't recall the name), Staples brand, and even a few nicer ones like Sony. I have been 100% successful with verbatim. Not just in burning, but in playback as well. You pay more for Verbatim, but can find deals at places like OfficeMax and the like from time to time where you get a 10 pack spindle for $15. ALL of the other brands I've tried had burned "coasters" or I had issues with playback (transitions from one layer to the next were where they usually fell short).
Sirquack mentioned RiTek, but finding a source for their dual layer discs can be tricky. From what I've heard, they are as good as Verbatim, but cost less.
