In The Why-Didn't-I-Think-of-That Department: Playground Finder

Use the Playground Finder to find good places to take your kids to play, they're reviewed, rated and you can add new ones as well.

An excellent and growing resource that I'll definitely be using. Now if they only had one for dogs as well.

[Update: Upon closer inspection, its not US-based, its Australian and New Zealand based which makes it a touch less useful.]