From Adafruit:

Welcome to the Black Friday sale – 15% off plus all the free items & shipping as you shop! Use code: BLACKFRIDAY on check out. We thought about doing flash sales or complicated codes but that’s a lot of frustrating hoop jumping for everyone, so we came up with what we think is an amazing deal that is straight forward, no stress and valuable – a 15% off discount anything in stock and lots of great free things automatically depending on how much you order. 

We are currently offering a FREE Adafruit Perma-Proto Half-sized Breadboard PCB for orders over $100, a FREE Trinket 5V for orders over $150, FREE UPS ground (Continental USA) for orders $200 or more, a FREE Pro Trinket 5V for orders over $250

From Sparksfun:

On Cyber Monday (12/1), everything in our Actobotics category is 20% off.

Next on 12/1/2014, we are offering hourly flash sales from 7 a.m. to 7 p.m. Mountain Standard Time, with 30-50% off on some of our most popular products.

These items have been hand-selected by our employees and are some of our favorite designs! See below for the complete list, so you can plan ahead to snag these great deals.

• Flash Sales are ONLY valid during their time window. If an item is sitting in your cart and the flash sale for it ends, the price will go back up!
• There is no combining flash sale orders throughout the day.
• Flash sales are a “while supplies last” sort of deal (which means no backorders!) - so get ‘em while the getting is good.... (list of flash sale items)

From Servocity:

(Full pdf flyer for monday's sale) Two random orders from monday will recieve a "golden ticket" worth $500 of actobotics parts.

From Robotshop:

(Full list of sale items available friday through monday) Free hexbug nano with every purchase.