Selected colors of the Logitech M325 cordless mouse are on sale for $12.99 + tax at staples.com. They will ship it free to your local Staples store for pickup (this works well for me since there's one on my way home from work). This is a pretty nice cordless mouse with a micro-step scroll wheel and wheel tilt switches (I already own two of them).
The ones on sale are:
http://www.staples.com/Logitech-Wireles ... uct_221264
http://www.staples.com/Logitech-Wireles ... uct_229908
http://www.staples.com/Logitech-Wireles ... uct_221263
http://www.staples.com/Logitech-Wireles ... uct_221261