Okay a few places you have to visit:

In Addis: Sheraton - Pretentious patrons, beautifully designed, completely out of place.. however you have to visit it just because it's one of a kind in Africa.
-Azmari beyt - Specifically toul-toul'es azmari beyt. She is one of the best in town and speaks passing English as well.
-Abesha restaurant has one of the best 'ethnic shows' in Addis. They present a range of dances and costumes from various tribes.

The beggars on the street are a shock for the first few weeks. You should try not to give them more than 20c each (a loaf of bread), or you will definitely find you'll deplete your funds in a very short period of time. Unfortunately, there has also been a case of organized begging. Their 'pimp' would literally cut the legs of the children & have them beg at certain parts of the city.
Judging from your various updates, you seem to be getting around and handling Addis well.

If you plan to travel outside Addis, Baher dar, Axum, Lalibella, Harare are all a must. If you have the time, the south and south western areas contain the least 'advertised' tribes, and are definitely worth the trip (e.g Gambella region)
If you're going to shashemene, stop by Langano & wondo genet. Lake Langano is pretty much the only body of water that is safe to swim in. It's a dirty brown colour, which are only minerals that is extremely beneficial to your hair/skin. In Langano there are 3 resorts. Wabe'sheblla, bakelamola & a new one Bishangari (bishangari.com). I highly recommend bishangari. It's on par with the Sheraton: something that hasn't been experienced in Ethiopia.

Lastly, enjoy the food!!! Most of seemed to have been mentioned in previous posts except for the wide array of fruits. Personally I loved waking up to drink avocado, pineapple, papaya, guava, orange & carrot. All of them fresh & organic!!
Also make sure you try 'geshta.'

Have fun & be safe!
Kream