Rainfest 2012 will be taking place over at Neumos in Seattle, WA, during Memorial Day Weekend (May 25th-27th). One of the biggest hardcore festivals of the year, this years headliners include: H20, Trapped Under Ice, Bane, and more. Full line-up and ticket information can be found in the replies.
I still have not been to Neumos yet. I'm not a super hardcore guy, but this might be fun..
Easily one of my favorite venues, especially 21+ shows when you can take your drink anywhere. I won't be attending Rainfest (only like 2 bands I'm interested in seeing), but any excuse to go to Neumos is a good one.