7 cups blueberries, divided
3 cups sugar
juice and finely grated zest of two lemons (need about 1/4 cup of juice)
Mash about 3 cups of blueberries in a much larger pot than you think you'll need. Add sugar, lemon juice and zest, and the remaining blueberries. Bring to a boil; turn down to medium heat and boil about 18-20 minutes, or until thickened. Keep stirring and take care not to let it burn on the bottom. Skim off any foam on top; pack into jars.
Really, that's it.
I do this as a refrigerator jam, as I don't can. If you do can, I'm sure you have sources which can tell you how to do that safely.
We've picked 40 lb. of blueberries so far this season. I just realized that we ran out today; we've frozen or eaten everything (or baked, or jammed, or what have you.) We've just decided to go back out tomorrow and pick more. I get the feeling that I'll be making a lot of blueberry jam with frozen berries this winter!