The SALSA sale is amazing. It is only for cast members on the first day. After that, you can bring up to 5 guests. There is tons of Disney merchandise for up to 90% off.

There is also one day where they sell just pins for like $1. It is the best because even if some of the pins aren't the best, you can buy them and still trade them for better ones. They have this sale once in the summer and once in winter. It is set up under a couple of tents on the far side of the EPCOT parking lot. I am not sure when it is going to be this year, but I will keep you posted.