My sight-reading improved very significantly over the past year. I went from having to really "figure out" notes, to being able to recognize chords and sight-reading a melody line with ease. I remember one day I tried sight-reading Chopin Etude 25/2 and I was able to sightread the right hand almost at full speed (without left hand). I was looking at the page the entire time, and this was probably the first time I truly felt that I was "sight-reading." I still have a significant amount of difficulty sight-reading for two staves if I'm trying to play the piece at a quick tempo. If I'm sight-reading a piece that is meant to be played fast, but is too complicated to sight-read at that tempo, I will sightread hands separate, which gives me some of the satisfaction of really playing the piece. I might then put hands together at about half speed. Examples of pieces I did this with were Chopin Prelude in G Minor (tough piece at tempo.)
I can sightread fairly well Chopin Nocturnes at a slow speed, and accredit Chopin with a lot of my sightreading improvement. However, I find it quite difficult to sightread Bach, which I guess just means I need more practice. I have had less experience with Baroque than any other style of music, which definitely affects my overall understanding of it and ability to sightread. Anyway, I'd say just sightread music you like, and try to keep your eye on the page. The less you look at your hands, the better.