Everyone has their own way of learning to sightread or keeping up the skill. I found this site through a search engine and I'm having a blast getting my reading chops up to speed — Sight Read This! - Music Sightreading Skillbuilding. It's pretty well organized and some of the melodies, especially the upper level ones, can get pretty challenging. I'm also using this to work on transposition. There's a minimal fee, about $5.00, but that's cheaper than some method books.