We had a cold spring, so berry fruits didn't get going as early as normal, but with a hot and well-watered summer they have produced massive amounts of fruit all in one go.
As I said in another thread, if wild-picking, do something with them as soon as you get home because they could go mouldy overnight even in the fridge. I'm a bit of traditionalist and I really like crumbles or pies or jam, but if at a loss just stew them lightly and put them in the freezer - they will be good for about 3 months in there (although go a bit mushy, hence the stewing them first so they're more of a sauce), and a simple dessert involving blackberry sauce out of the freezer can be a perfect reminder of summer once the days are short.
Or as others have mentioned, there are plenty of ways to either preserve them in alcohol or use them to make alcoholic beverages.
If you live in an area where people have apple trees and put boxes of apples out front for people to help themselves (and there's also a good crop of apples this year), then I'd suggest a job lot of blackberry and apple crumble which can be divided into portions and frozen. My parents often make crumble using a glut of late summer fruits from their garden, which goes in the freezer as fruit crumble - 30 minutes in the oven on 180C from frozen, serve with cream or custard or ice-cream - late summer dessert in winter (I was still scoffing home-grown and home-made plum crumble in the middle of January) - can't be beaten imo.