It may be too hot to bake these, but if you get up early enough, or you have central air, these are a fun breakfast for Fourth of July.
I first made these as just blueberry muffins a few weeks ago when I got all those blueberries on sale, so if you want to only use one or the other kind of berry, be my guest. You could make them with chunks of peaches and raspberries, too. Oooh. That would be really good.