Django already includes a markdown filter (in contrib.markup), but I nonetheless rolled my own Markdown for Django mini-app. The main benefits are link integration with django models (by using generic model queries and getabsoluteurl), a documentation generic view that handles language switching and a nice macro facility for markdown. Macros are a usefull way to extend markdown by writing Django template snippets that are called whenever the users calls the makro in his markdown source.
It was formerly part of the CMS project, but I think it's usefull in it's own and so much better put into the stuff pseudo-project.
