I've been lucky enough to hike around in the Simien Mountains on several occasions as well as climb Ras Dashen, Ethiopia's highest peak, twice. I wanted to recommend http://www.habeshaadventures.com to you guys as a great way to get to Ethiopia, learn about the culture, volunteer, and of course do some epic trekking.

also, I'd be more than happy to answer any questions you guys have about trekking in Ethiopia, climbing Ras Dashen, or just traveling in Ethiopia in general.....I've been living in Ethiopia for a couple years now so I should be helpful.

For more info on the Simiens including detailed route descriptions check out: http://www.habeshaadventures.com/simien-mountains-national-park-ras-dejen