My partner and I spent 1 night at Hotel Avenida in May 2012. Don't be mistaken by the name "hotel", it isn't. We ended up staying here because we came across it after a long night-bus from La Paz. We figured it was only one night, so we would cope, and we didn't expect much for the price.
We paid 60 Bolivianos for a twin room (big beds), with a shared bathroom - a very good price. The room was very very basic, and cold. As the beds were more like doubles than singles, we shared a bed and put all the blankets on one (about 7 blankets!), which kept us warm.
The bathrooms were basic, with no toilet paper, but the shower was surprisingly hot. Although, as the floor tiles were so cold, you soon cool down.
No wi-fi or breakfast, which seems to be the common trend in Uyuni. Walking distance to everything, including bus station.