In reply to BruceM:
Hotel El Pilar in Benasque is good and not expensive, plus 2 campsites a couple of km up valley, and a free camping area above them. Make sure you boil the water in the latter. Early morning buses up Valhibierna and the main valley are useful. Free dossing hut at the former road end. Camping on the hill is allowed from 8pm to 8am but not for more than 1 night. Estos Hut below the Posets is nice, Renclusa below Aneto is awful. Aneto is doable in a day using the Valhibierna bus, as are Pico Margalida and the traverse of Pico Vallibierna, both nice scrambles. The Cresta Bardamina-Paul below Posets is the best scramble I've ever done, about Mod, sustained and wildly exposed, on ace granite. Have a great time (if that's where you go).