I really liked Irgalem because the town is in the middle of a forest south ofAwassa, surrounded by coffee plantations. The tropical setting is really pretty and the Sidama huts are very quaint.
I was lucky enough to go there for the Sidama New Year celebration, the Fiche Festival. Despite the fact that every year the date is selected depending on the moon's position and astrological predictions (the Ayantos), it's possible to book your ticket in advance as it lasts several weeks. Aside from this festival, you can simply visit the local tribes.
It is worth booking a hotel because the region is cluttered by the Sidama people who return to the region (there are 2.5 million of them in Ethiopia, which is 10% of the population!). The festival starts with a large meal eaten between neighbours, during which the ground is blessed with fistfuls of wassa, a traditional dish made with butter and roots of enset leaves, a tree which grows there.
The following day, nobody works, and the children are sent from house to house to celebrate the new year. During this time, young girls and boys organise traditional songs and dances throughout the markets. The atmosphere is very festive.