In the past few months, I've found myself signing up for more and more email lists from local restaurants, and there has been lots of good information from them. I've been on the Dave's Fresh Pasta list forever, and I love getting their lists of classes and learning what they have on special in the store. The Excelsior email list has been helpful in highlighting any deals they have (because I don't have the cash to eat there just any night). JP Licks is a good one to learn about the monthly flavors. Grotto/Marliave's list is a great place to find out about their special events (although I've found that I periodically get removed from the list and have to sign up again).
Which email lists have you found most helpful?