You might look at bootstrapworld.org, a project to teach functions and programming to middle schoolers. (I mentioned it in another post, but it's directly relevant to the question.) Their after-school programs (and summer camps) are interesting because they also teach testing (facilitated by functional code) and code reviews (students present their code in a Q and A session) and use pair programming.

Microcontrollers, notably Arduinos (or PICs or BASIC stamps, etc.) are the modern-day equivalent of the Apple //e or IBM XT. I'd say go with the Arduino since it has the widest support in terms of kits, tutorials, ready availability and user community.

(On the historical front, people like David A. Lien (Level I BASIC manual) and Bob Albrecht (BASIC: A Self-Teaching Guide) deserve huge credit for their fine self-teaching/programmed texts for learning BASIC on vintage microcomputer and mainframe systems! Not to mention David Ahl, Creative Computing, BYTE, and all the other awesomeness of the microcomputer era. Back in the day, it was assumed that anyone who got a microcomputer, whoever they might be, would undoubtedly and inevitably learn to write programs for it!

Dive Into Python and its ilk are OK, but I have yet to see something that is nearly as good as the old self-instruction books on BASIC.

For that matter, even old-school books on 6502 and Z-80 assembly language (e.g. Lance Leventhal and William Barden, Jr.) were written clearly and with the assumption that anyone could learn!)

In addition to MIT and CMU, which have already been mentioned, Berkeley and Stanford have their introductory CS courses on youtube (and iTunes.) I particularly like Stanford's CS106 with Mehran Sahami. If you want something more middle-school-ish (or scheme-ish) and connected to algebra and functions, check out http://www.bootstrapworld.org/ (founded by a professor at Brown) (Seeing all of those parentheses reminds me of the book that taught me Lisp, David Touretzky's Lisp: A Gentle Introduction to Symbolic Computation, PDF at http://www.cs.cmu.edu/~dst/LispBook/, which should really be brought back and updated for DrScheme!)