Just stumbled on this thread (again?)...
This page has a list of some good deals on anime DVD (sets):
http://www.dvdtalk.com/anime/
Rumor: DeepDiscount may do another 20% off sale again (that's 20% on top of their usual 30-50% discount). For more info, see
this thread on Anime On DVD.
Also, RightStuf is doing a special sale all the time... this time it's Viz (which is good if you want to buy Naruto or Bleach DVDs):
http://www.rightstuf.com/
A complete overview of all past sales can be found
here. Also check their weekly specials. While not all of them are great deals, some of them are not so bad.