Boing Boing -- Best. Blog. Ever. If you like science, art, literature, technology, and culture, then Boing Boing is the blog for you. The interests of the contributors are wide-ranging (steampunk, evolutionary biology, design, geek culture, physics, music, privacy and copyright issues) and the rotating weekly guest bloggers bring more in-depth looks at specific topics (New Orleans jazz society, "dangerous" chemistry). You'll never be bored with BoingBoing around.
ShelfTalk -- Reading & viewing recommendations on various topics from the librarians at Seattle Public Library. Want to read more vampire novels? Watch David Tennant? Discover French fiction? Their suggestions can get you started.
On An Overgrown Path -- A former BBC classical music radio DJ covers the classical music world. One of his major interests in the intersection of music and spirituality and the expression of religious faith through music. I've discovered a number of exciting works and composers through this blog.
ScienceBlogs -- The name says it all. Check it out.