My step-father-in-law introduced me to Sudoku logic puzzles last weekend and I've been compulsively obsessed ever since.   Here's the URL:

http://www.sudoku.com.au/

There are 3 new puzzles every day, one easy, one medium, and one hard.  The easy ones I can do in less than 5 minutes.  The hard ones I try to finish in less than 20 minutes, but I've spent over an hour on them before.

These puzzles have everything about logic puzzles that I loved as a kid without most of the bad parts.  There is no math to do, yet it's number oriented.  Most of the work is "process of elimination" oriented.  It's very visually stimulating.

The biggest downside I've noticed so far is the first ~10 minutes of grunt work that goes into a hard puzzle.  Being a programmer, I'd love to just code up an algorithm to do a first pass analysis for me which would save a ton of time, and eliminate the normal human mistakes.  I'm not sure how that would affect the "fun factor" though.