Shit my kids ruined - makes me feel good to know that other people's children are just as lively as mine (if not more so). Your parenting skills have absolutely no impact on the heat-seeking-missile-like focus children have when setting their minds to something.
http://www.shitmykidsruined.tumblr.com/
Huffington Post - good for a laugh, tends to be USA-centric but their picture galleries are great.
http://www.huffingtonpost.com/
This one is for you Emma:
http://itmademyday.com/2010/06/03/funny-win-stories-brandon/
Nice funny little bon mots.
...
that is it for now, but will add to the list when suitably funny sites are found.