There are a couple of sites I go to regularly for humour of the quasi-literary sort.
The first is aptly named: Passive-Aggressive Notes dot com. It's kind of like that "Post Secret" site that was so hot a couple years ago (and still might be, for all I know) but much funnier. People take pictures of p.a. notes other people have left. The comments are, predictably, mostly hilarious.
The second is one I've mentioned before is The "Blog" of Unnecessary Quotations. As you can see by the "quotation" marks, it's not "really" a blog. But it is a consistently amusing look at the terrible license taken by people, people with a certain authority or level of administrative power, who can't write.