These are the ones that I know of that are usually held in the northeast. Some might be out of your range, but I figured I'd list them anyway.
- BattleCry@WPI in Worcester, MA (confirmed for 2013)
- Rah Cha Cha Ruckus in Rochester, NY (no date/confirmation yet)
- Bash at the Beach in Old Lyme, CT (no date/confirmation yet)
- Monty Madness (confirmed for 2013)
- Bridgewater Raritan Battle Royale in Bridgewater, NJ (no date/confirmation yet--not sure if they'll have this year as they hosted a MAR district event)
- Where is Wolcott in Wolcott, CT (confirmed for 2013)
- Ramp Riot in Ambler, PA (no date/confirmation yet)
- Brunswick Eruption in North Brunswick, NJ (no date/confirmation yet)
- Duel on the Delaware in Salem, NJ (no date/confirmation yet)
- Mayhem in Merrimack in Merrimack, NH (confirmed for 2013)
- Pascack Panda-monium in Montvale, NJ (they haven't held it in a few years but are considering reviving it for this year)
- River Rage in Manchester, NH (no date/confirmation yet, but it's the longest running off-season so it's pretty safe to assume it'll be happening)
- Beantown Blitz (linked above by Brandon)
Those are the ones I know of. I'd keep an eye on the Off-Season Events section on here. New ones get started every year, as well.