Hackety Hack still exists http://hackety-hack.com/

I've taught several people quite new to computers Ruby and HTML, I've found the hardest thing they try to grasp is logic, drill into their head how conditionals and boolean logic work - it's needed everywhere.

EDIT: I can't stress this enough, I've had people where I thought I've made a break through, they seem to grasp it, then two weeks down the line I look at some code they're trying to debug, and it's like they completely forgot how flow control and conditionals worked.