BAZAAR in Calle Libertad, Madrid.

Very reasonable (we paid 40euro for 3 of us for 3 courses each!) and a wicked atmosphere. Trainee chefs a la Jamie Oliver hence price. You can't book, so go early (well, Spanish early anyway) if you want to be sure of getting a table. It's in the gay area (Chueca) and there are loads of good bars nearby too.