Looks to be a transaction with a lot of little outputs. I'm guessing CoinAd or DailyBitcoins or something like that. Either you used one of them and don't remember, somebody else used your address on one of those sites and didn't tell you, or my guess is wrong.
Well, now that you talk about it I did fell for the CoinAd April Fools joke and used this one address
Also, a moderator might fell it's needed to move this thread, but I couldn't find a better forum to post it.