I recall there being a thread last year that everyone could mention the apps they've came across in iTunes today that were discounted today or made free entirely. I don't want to know that every single fart app went from 99 cents to free, please only post apps you find useful and that others would realistically benefit from.
By far the best deal I have found so far is that Sketchbook (iPhone) and Sketchbook Pro (iPad) have both dropped to 99 cents (normally $2.99 and $7.99 respectively).
The Navigon Apps have all received a $10 or so discount.
As far as just neat toys go, Wind Tunnel and Stereogram3D have both been made free for Black Friday.
I remember they did that last year too and I bought like five games. Outside of the need for speed games, I don't think I played any of the others more than two or three times. It taught me that I'm to avoid any games involving a d-pad and digital buttons on the iDevices.