i can think of two sites which might help you out.
the first is called Findory, which scans through many many sites, and as you read more of the articles you find interesting, it serves you with more of the same kind.
however, it might give you more news like sources.
the second site, which is quite new, is called Qoolsqool, which is all about educational resources online.
ppl sumbit links to all kind of educationl resources (mostly free, like articles, presentations, audio books, books ect.) in all sort of subject, and people rate them by saving those links in their sqoolbag or writing comments on them.
hope this helps,
happy learning.