I totally agree with JWPalmer about the tulip poplar tree. I planted one about 3-4 years ago and it's doing better than any other trees I've planted. Seems to be very disease and pest resistant, and it's growing pretty fast. Plus, I've seen mature tulip poplars with thousands of bees on them, and there's one along a local hiking trail that looks like a redwood it's so big. This spring I planted 10 more tulip poplars on my land--that's how much I like them. I also like the American Basswood (Linden) tree for bees because it has a massive amount of flowers when it blooms; but I'm finding it a bit harder to grow because the Japanese beetles like them too.
Just for fun, I outlined 1/4 acre plot here on my property and played around with it. This is what I came up with in about 10 minutes. You could do something similar (I used Google Earth)--just make sure the plants are well-suited to your site.
With this scheme, I've put trees on the north end so they don't throw shade on everything else as they get bigger. I tried to put the lowest-growing plants on the south side, progressively moving to taller plants as you go north.
And the bloom times look something like this:
March-April: Hopefully you've got various maples, dandelions, redbuds, etc. growing wild in your area.
Early May: Blackberry
Early May: Tulip Poplar
Early May: White and Crimson Clovers
Late May: Yellow Sweet Clover
Late May: American Basswood
Late May: Ninebark
Mid June: Borage
Mid June: Cosmos
Late June: Milkweed
Early August: Goldenrod
Early September: White Snakeroot
Mid September: Aster
Easier said than done planting all of these (also expensive), but this should provide some kind of food throughout the forage season. Of course, 1/4 doesn't really make much impact (except for the trees once they mature), but it doesn't hurt. It's also enjoyable and keeps some of the bees nearby so you can watch them work.