SimplyBibTeX is an application to share and hold BibTeX bibliographies. One can add, edit and remove entries from bibliographies online or upload complete collections. The system uses a very simple but effective template mechanism. Users and coworkers can subscribe to RSS 2.0 or Atom feeds in order to get notified about changes.
Tartan is a text parsing engine targeted at wiki text. The syntax specification is defined in YAML in the form of regex-based rules. It supports layering and multiple output types. Rules for Markdown to HTML are included, with optional layered extensions for tables. It is implemented in Ruby, but looking to have implementations in other languages.
WikklyText is a Python-based wiki and modular library for creating custom wikitext rendering applications. Its wikitext engine is compatible with the TiddlyWiki markup language. It functions equally well as a wiki-on-a-stick or as a multiuser wiki behind Apache. It includes a Drupal plugin as well.