Credit card numbers estimated to be in the hundreds of thousands, if not millions, have been stolen. This is due to a credit processing company called Global Payments being compromised. The company found out they were hacked in early March (why are we just barely hearing about this?) and they haven't released how much information has been stolen just that "card data may have been accessed" (nice corporate two-step there

You can read more about it here:
http://money.cnn.com/2012/03/30/technology/credit-card-data-breach/index.htm?hpt=hp_t1
http://online.wsj.com/article/SB10001424052702303816504577313411294908868.html
So keep a very close eye on your credit and debit transactions to make sure nothing fishy is going on. Also tell other people you know so they are aware.
Edit: This does not appear to effect people outside the US, though if you used a credit card either online with a US company or on vacation here any time this year yours may have been compromised.