I went trolling at our local Microcenter store's Maker section. Besides $14.99 Arduino Unos, I was surprised to see additional items added to their lineup:
First is the Digistump Digispark line. Started on Kickstarter, these boards are wonderful for smaller projects both in low prices and big flexibility. The board is $9.99 and they have a full line of shields.
Tinkerkit line. Formerly only available on the www.tinkerkit.com and Arduino.cc stores (and priced in expensive Euros), now we have them in the US. While not as good a value as other parts, they have them including some sets and individual sensors. I did NOT see any of the connecting cables which would limit the ability to use them. Get your Arduino Esplora at Radio Shack and consider adding Tinkerkit components.
SO Microcenter is becoming quite a player in the Makerspace. I would like to see them organize their products so they are easier to browse. But overall I'll take quantity over quality.