Mars Bar
to add to
QatarA340's list. The W, Moevenpick, (no beach at either) other than that, not much to see and do here, as already mentioned, the Malls, the Souq is unique and worth a visit. thats day 1
as for day 2 have a look at the links
YouTube - Spotlight on Doha
also you can go Dune Bashing for a day out with a local tour operator.. it is fun, but after a few years it gets old.. but it is fun.
YouTube - Dune bashing Qatar summer 2008
Poisoned by Compromise
Krunch