As a follow-up to our DVD Picks this week, the 20% off sale running at Deep Discount is live right now and is running through June 22nd! Just go to their site, load up your shopping cart, and use any of the one time use coupon codes listed below. You can use each code once, but you can place more than one 20% off order. This sale has helped me build my DVD collection considerably over the past years. It's a great chance to pick up some Criterions for cheaper than usual as well.
If you hit the site and are completely overwhelmed and have no idea where to start, I always hit the thread for the Deep Discount sale at DVD Talk. People are always posting what they bought there and it should help you get a great idea of stuff to get. One important thing to consider is getting together with some friends and doing one larger order and pay for upgraded shipping and split that extra cost between everyone. They have flat rate shipping at each level, and upgrading your shipping tends to get your stuff shipped out earlier. Granted, I ordered Student Bodies for $8.18 with the free shipping and it's aready shipped, so do what you will.
DVD Planet also tends to run a concurrent sale that's going right now. They sometimes have Criterion DVD's cheaper than Deep Discount, so they're worth checking out as well. You can find out details at this DVD Talk thread.