Using Snippets, Plugins and other Add-ons downloaded or installed with the Package Manager
Snippet-speak, extending the Core via Plugins, and integrating with other applications.
Support topics for Snippets, Plugins and Other Resources in the Download Repository. (Specific categories below)
Dynamic menus builders, link generators and content navigation.
Make or re-use content found in your site. Includes user blogging (Ditto), commenting (Jot), text summarization or formatting and other similar tools. Also includes "front end" content creation and editing (including QuickEdit).
Anything dealing with users, including login, retrieving user info and personalization systems.
Community-builders including Forums, Polls, Calendars, Address Books and more.
For all RTEs (Tiny, FCK, Xinha, XStandard) and File Browser related (MCPuck and its future replacement)
All content-search-related code including AjaxSearch, FlexSearch and others.
E-commerce, E-Marketing & SEO, and anything else you need to create and/or monetize site traffic.
Forums, CRM, etc. and the code that helps to bridge modx to third-party solutions.
Support for outputting or managing, pictures, slideshows, podcasts and other similar media (including "helper" or utility code)