Artlandia SymmetryWorks - Adobe Illustrator plugin that lets you easily creates and interactively edits symmetrical patterns and designs. Available for both Mac OS and Windows.
CVally, Inc. - Offers three plug-ins for Adobe Illustrator. FILTERiT, Xtream Path, and Silhouette.
Graffix - Choice of multiple plugins for Adobe Illustrator 7 and above for download.
Hot Door Inc. - Offers various plug-ins for Adobe Illustrator including CAD, simulated 3D drawing, and symbols.
ILLOM Toolbox 1 - Various plug-ins tools like Search/Replace, Selection tools, Time tracker, Type Style Library, Transform and Magnet tools, and a game as a plug-in for Illustrator. [Mac/PC]
Magisign - Produce signs in 4 steps using Adobe Illustrator.
MapStudio Web - Plugin to draw orienteering and other maps. The plugin is only for Macintosh.
Network Symbol Library Plug-in - NetZoom Symbols is a powerful plugin for Adobe Illustrator to easily create detailed and accurate network diagrams, network documentation, proposals and presentations using over 35,000 vector network equipment symbols.
Panopticum - Offers plug-in modules for Illustrator for creating complex geometrical patterns and vectorizing color raster images.
Stephen Vincent's Plug-ins - Offers various plug-ins with a theme of creating complex paths in Adobe Illustrator.