Here are two of my favourites:
Arts & Letters Daily, a site that collects articles, book reviews, and opinions about such diverse topics as philosophy, science, religion, history, art, literature, world affairs, et cetera. The site presents these with a short blurp followed by one or more links for further reading. Its motto is "VERITAS ODIT MORAS", which translates as "Truth hates delay." It also has a lot of interesting links to other sites of equal interest. Strongly recommended if you want to keep up with matters intellectual.
SciTechDaily, a site comparable to the previous one I mentioned, but with the emphasis on - not surprisingly - science and technology.