My daughter has always been a good puzzle solver. She's freshly 4 and she can do a 100 piece puzzle. She LOVES these: http://magnatiles.com/ they're not really puzzles, but I think they encourage that kind of thinking. My in laws got her some at her third birthday and she'll build massive structures out of them. They're kind of pricey but they're a great toy for open ended play.

Ooh oops I see someone mentioned these as well. They really are great. smile

Z - 01/23/11 and O - 05/12/13