The minibuses are quite cheap to go around, and they are very busy in the mornings and at the time when people come back from work. When you don't know the fare, ask the person next to you as the guy taking the money might not be the most honest guy you will meet.
A good place to have a beer, although it does not close very late at night, is not far from Bole in the city center. It is a local place where you can eat while sitting on the classic Ethiopian plastic chairs, have a good coffee in the small hut with all the other customers, or enjoy a beer in the garden. Here is the address as indicated on the bill: Bole Kebele, behind Millenium. Tel: 09 111 648 12. Just ask around for the Kebele (means something like "local place").
Pretty much non existent.