Here's a web sampler of Marchetti and O'Dell's latest book, which you can buy at Heinemann and here's a blog written by the two of them.
Articles/blogs about using mentor text:
Using Mentor Texts to Motivate.... and 8 Tips forTeaching with Mentor Text
Suggestions for teaching students to read like a writer: Moving Writers about scaffolds and Moving Writers Part II
For authentic models of analysis: Problematic favs and the AV Club
For models of essays, check out Katherine Bomer's website. (Warning: this is not essay in the boring sense.)
Graphic essay and here are three graphic essays from the Chicago Tribune
Hint fiction or flash fiction or twitter fiction or flash essay/micro-essay
Try this one for cause and effect or this one -- but then are they also compare/contrast or problem/solution or argument?