I also got this email. I suspected it due to the Gawker incident, although I wasn't sure. I wish they had been a little bit more specific.
I also got the email from hint.io, but it was marked as spam by GMail.
I was really glad when I found out about the incident that I used a throwaway password that wasn't the same as my GMail. I've been keeping track of more of my passwords with KeepassX, although I still use the same somewhat secure password on sites where it doesn't matter.
As a side note: I'm trying to brute force/crack my hash to test how secure my password is. I'm using John the Ripper with the command line:
john -session:testing -incremental test.txt
So far, I'm 17 hours in at about 600000 c/s and it still hasn't been cracked, so I feel somewhat secure about it, although I realize DES is considered insecure.