I think cosmos and nasturtiums are easy choices for direct sowing into your garden.
One year I thought it might be a good idea to try some marsh marigolds. That wasn't one of my better ideas. Even though it grows easily and attracts bees, it is more like a pretty weed. I find it too invasive. I haven't decided what I am going to do about it yet.
This web site from the University of Georgia has some great info about bees
http://www.ent.uga.edu/bees/beekeeping.html
I'm not sure if bees really prefer a certain color flower. Since I keep bees I make sure I have a succession of many different flowering plants so there is always something in bloom for them.
That being said, if I want to save my tomato seeds for a certain variety, I always bag the blossom. Can't be too careful.