Check out this link for advice on hanging a barn beam to drywall.
http://www.handhewnbeammantels.com/page/page/3122456.htm

Thanks for your quick reply! Unfortunately, the beam in question is not thick enough to notch out for a 2"x4" support. I am looking for a long steel "bar" that would be screwed to the wall with steel bolts placed intermittently so that the beam could be pre-drilled and inserted into the bolt extensions. Hope I'm making sense here...

You could buy a floating shelf at Ikea and use their hardware. This is what I am thinking of doing for my large floating beams in my kitchen. (they weigh a ton!)
http://www.ikea.com/us/en/catalog/products/70103622/ they have longer shelves as well, I use these shelves (I have 6 of them) and can hold alot of weight, I think this is the concept you are thinking of.

michigammemom, you nailed it! Off to the hardware store... Kelli, thank you for your reply, too! I actually really like the IKEA shelves in gloss red and may use those elsewhere...

Don't know if you understood what I mentioned above - you use the hardware for the shelves -
The hardware is around 4' to 5' long metal plate that has 4 metal poles extending out. You screw the metal plate to the wall (about 14 screws) drill out the wood beam where the metal poles sit inside. After you secure the metal plate to the wall you slide the wood beam onto the metal poles. Floating shelf.

Good luck, let me know how it goes, I need to do the same thing but with 3 beams!

Oh, Kelli, that sounds exactly like what i'm looking for, but the link sent me to a shelf with different hardware. Will look more closely at IKEA site...thanks for clarifying! Will try to upload photos post-hanging. I'm in a 200 year old carriage house and trying to get a little edginess to the kitchen shelving, but not too modern.

LOVE IT! Would love to see pic!!!!!