Here's a link to a rich page of Writing Operations distilled, organized, & presented by Susan on her GMU web site.
Susan's entire collection of resources for writers and students - "Bouncing Off Walls" (sub-head "indoor sports for poets") - merits serious exploration. For now, I'm including the page on Writing Operations here because many of the exercises can be adapted for collaboration and collage. (Susan includes a notation besides those that suggest collaboration, or involve altered text or collage.)
The page is a handy list of definitions/explanations of various fun writing operations: Anagram, Lipogram, Cancelled Text/Erasure, Perverse, Breaking Words, N+7, Boolean Poetry, Analytic Dictionary Definitions, Translexical Translation, Exquisite Corpse Cut Up, and others. As Susan points out, many of the terms are defined and included in the Oulipo Compendium, but this page/cheat sheet/list sure makes it easy to browse and learn and pick one that might be fun.
[Note from the Department Against Self-Promotion: Susan doesn't know that I am featuring the page here. We've discussed how to get some of the information from her excellent collection of resources at GMU onto this blog, but I like this collection so much I simply decided to jump right in and link to it. Why not?]