Buy your tomatoes! Now is a great time to find them at your local farmer's market on the cheap...be sure to ask if they have #2's!
Set up two pots. Boil one, put ice in the other.
Set up your work space for after the tomatoes come out of the water.
Once the water is boiling, drop the tomatoes in for 2 minutes. For larger tomatoes or heirlooms with quite a few rough patches on them, I'd leave them in for 4 minutes. You can tell they are ready to come out of the water when the skins crack or start to peel off.
With a slotted spoon, transfer them into the pan with ice water. This makes the skins come off easier, and makes them easier to handle as well.
Put the iced tomatoes in a bowl, move them to your work space. For tough stems, I simply cut off the tops of the tomatoes and peel from there. Some stems will come right off. Cut off rough patches, and the rest of the skin should slip right off.
After peeling, dice into large chunks, and transfer into freezer quality ziploc bags.
FREEZE! They will keep in your freezer for up to a year.