Now's the time to scout for blind material. Cane doesn't grow just anywhere and modern farming techniques don't leave many whole corn stalks behind. You might want to contact a farmer now to save you a few rows. Just make sure the corn goes to the birds or squirrels, though.

Take care of your waders now and they'll take care of you next fall. There are plenty of commercial applications that will keep the exterior surface soft and pliable and they should be used before you hang them up.
And if you noticed a leak last season find it and fix it now. It won't heal itself over the summer.

If you ever hunt small sloughs by yourself without a boat you might want to consider a belly boat. That's basically an innertube with a seat. Many come in Advantage camo and work well (and more often, actually) for small-water fishing. Buy one now, fish in it to get used to it and you'll be a veteran next fall who can access out-of-the-way sloughs your buddies can only dream about hunting.

If your duck boat doesn't double as a fishing platform be sure you ran all the excess fuel out of the engine. Might want to check the bearings on the trailer, too.

Make sure your blind, if it's cloth, wasn't put up wet with decaying vegetable matter in it. Spread it out so it can dry completely, clean it thoroughly and put it up until next fall.