The majority of native bees are solitary and ground nesting. They require sloping, untiled, sandy loam to nest in. This includes certain Leaf Cutter bees.
Mason bees and other Leaf Cutter bees are tube nesting. These will nest in pre-drilled holes in untreated wood. Larger bees require larger holes and deeper tunnels while smaller bees will need smaller holes and will accept tunnels that are more shallow (3 to 4 inches). Make your own, and include a variety of hole sizes. Just go down the line of different sized drill bits and see what you attract. Don't drill all the way through the wood!
Most of these bees mentioned above are only active for 4 to 6 weeks of the year and spend the other 11 months developing.
Carpenter bees come in two sizes. Both drill holes and make their own nests. The smaller varieties tend to nest in soft plant matter. Raspberry stems for example. The larger forms look more like bumblebees and drill right in untreated wood. That's not to say they won't nest in treated wood but untreated is preferred.
Bumblebees and Sweat bees are social and will be active all year except winter. Sweat bees sometimes nest in untiled sandy loam but there are types that nest in hallow cavities in standing wood too. Bumblebees tend to nest in former rodent nests and burrows. If you have some sort of rodent population on you're property then you're doing ok to attract them. To attract them simply allow a patch of grass 5' by 5' perhaps and let the grass go to seed. It usually falls over on itself and creates the perfect nesting spot for field mice to weave their nests and hopefully be used by bumblebees next year. Be aware you might have to weed the grass every so often. You Don't Want saplings to trees all growing there. Also be aware a population of cats can ruin your plans. Make a larger patch or go with nesting blocks. Nesting blocks, similar to bird houses, can also be placed out in tall grass and shady location. The entrance hole should be 3/4 an inch I believe, and inside should be a thin sheet of cottony fabric. Bumblebees like insulated nests.
Everyone has their own special list of plants and will tell you something different. I say go with as many native plants, in their native region, as you can. Thoughts on evolution aside, native plants are the ones that have been here growing with the bees far longer than anything imported. That's not to say the bees won't like a few of the imported plants, actually that's often the problem. A lot of the highly invasive plants tend to be high on the bee list. Honey bees tend to love a lot of the Asian imports that have gone invasive. Native plants at least have the benefit of being eaten by things and controlled by insects, many are even specific host plants to moths and butterflies. Plants have a habit of putting chemicals in their leaves and can only be eaten by a hand full of species. Why not go all the way and go for a general Pollinator Garden?
Here is a list as I see it.
Native Host Plants for Moths and Butterflies.
Milkweed, Butterfly Weed, Orange Glory Flower, Asclepias (Not Butterfly Bush!)
Joe Pie Weed (Eupatorium dubium, or E. fistulosum) other Eupatorium also good.
Black Cherry Tree
Black Eyed Susan, Cone Flowers, and Daisies.
Button Bush (Cephalianthus occidentalis)
Violets (Viola, native violets! ones that aren't regularly sold in garden stores.)
Dogwoods (Cornus florida) make sure it's a native dogwood!
Native Nectar Sources
Liatris, Blazing Star, Gay Feather
Sumac, Winged Sumac
Summer Sweet, Clethra alnifolia
Aster (Not Mums!)
Winterberry, Ilex verticillate
General fruit and vegetable gardens are also beneficial. Allow as many of the plants to go to flower as possible. Certain Apple trees aren't native to America but don't go invasive, and offer a bounty of spring flowers.