Houzz.com is the "biggest" site by far. I like
http://stylebyemilyhenderson.com for midcentury modern (and a fun read),
http://www.designsponge.com for DIY/hipster chic, and
http://domino.com for modern (and a little girly).
And yes, I read too many of these. And yet my house still is a disaster. So reading is not enough!