America’s spy agencies want to read your blog posts, keep track of your Twitter updates — even check out your book reviews on Amazon.

In-Q-Tel, the investment arm of the CIA and the wider intelligence community, is putting cash into Visible Technologies, a software firm that specializes in monitoring social media. It’s part of a larger movement within the spy services to get better at using ”open source intelligence” — information that’s publicly available, but often hidden in the flood of TV shows, newspaper articles, blog posts, online videos and radio reports generated every day.

Visible crawls over half a million web 2.0 sites a day, scraping more than a million posts and conversations taking place on blogs, online forums, Flickr, YouTube, Twitter and Amazon. (It doesn’t touch closed social networks, like Facebook, at the moment.) Customers get customized, real-time feeds of what’s being said on these sites, based on a series of keywords.

“That’s kind of the basic step — get in and monitor,” says company senior vice president Blake Cahill.