Briefly the WeBWorK module is an interface to a mathematics homework system with symbolic math capabilities. This open source system from the University of Rochester is called WeBWorK.
The WeBWorK module can be downloaded from the optional modules page on moodle.org: http://moodle.org/download/modules/. You will find some links to forum discussion here and a link to the University of Rochester WeBWorK page. You can find additional information by searching the forums here on the key "WeBWorK"