maybe make those boxes just show their headers, and when hovered over, slightly change color and expand to reveal the full text? I’d also simply make the whole box a link, but I guess others or you might disagree :P I just don’t like “click here” links personally ^^
a must (IMHO) is to mark the box of the page you’re currently on in some way, like you do in the top header…. of course, if you could find a stylish way to get rid of that duplication, that would be a bonus. make the header nav blocks colorful and bigger, expand with the full text – done? at least in my mind, that might work :)
the text in the yellow box is a tiny bit hard to read (on my monitor), a bit more contrast would help. with the blue box too, but to a lesser degree.
maybe the light blue from the header could fade over into the white? or the opposite, a little border/shadow.. dunno if that would improve anything, just something that occured to me. maybe that white background could use some very(!) light texture to it, too.
and consider using web fonts instead of images for headers! even using images instead of CSS backgrounds (and giving those images alt text) would be better, because with a website as this accessibility should be first and foremost. if the design is light, that’s okay… and yours is light in a very stylish way, but it’s not very nice to search engines or screen readers with those headers, so that would be my one real complaint.
well, and maybe that many pages requires a bit much scrolling… I think it might still work with a bit less padding etc. the font could be a tiny bit bigger, too, with less line height? maybe, it’s hard to tell without fiddling with it, so take all of this as just my 2 cents and good luck :)