Walmart - After Christmas 2012 Clearance

Walmart has some various sets on clearance, often up to 50% off.
Some of these items include the City & Star Wars Advent calendars.

Also, a few seen in person:
4431 City Ambulance ($9.50, reg. $19.97)
4206 City Recycling Truck ($14.50, reg. $29.97)
7961 SW Darth Maul's Sith Infiltrator ($27, reg $54.97)
7959 SW Geonosian Starfighter ($12, reg $24.97)

Some Dino & Ninjago sets are said to be on sale as well, but they're mostly cleared out from stores already.
Most sets aren't marked, so it might be worth finding a price check scanner on sets you like.

Kmart - BOGO50%

This week (12/9-12/15) @ Kmart:
Buy one get one at 50% off from the following themes:
Monster Fighters, Duplo, Star Wars, Lord of the Rings, and Hero Factory.

Target - BOGO50% City Sets & Games

This week (12/9-12/15) @ Target:
All LEGO City Toys & Games Buy 1, Get 1 50% Off.