ThinkGeek is having a summer sale with items as much as 75% off, including some LEGO stuff. The sale items are mostly accessories like brick lights and pens, but other LEGO products are eligible for a buy-one-get-one-50% off promotion. They don't really specify what all qualifies, so you'll have to play around with things in your cart, but it looks to LEGO sets and a few other items are eligible.
The BOGO is unlimited and stackable with some items already on sale. For example, buy Series 3 Minifigures in increments of two and end up paying $2.25 for each after both deals combine.
Other items of note:
-LEGO Alarm Clock $19.99 (was $29.99) 33% Off
-Brick Construction Shirt (child size) $2.99 (was $14.99) 80% Off
-LEGO Digital Video Camera $59.99 (was $79.99) 25% Off