Moodle has the ability to be integrated with a vast number of other systems. Some of these are already available as third party Modules (such as):
E-Learn Design has a great deal of experience in setting up integrations with Moodle, as well as creating our own.
If you have a need to integrate Moodle with a system not listed on moodle.org we are happy to create custom integration plugins for you. Quotations and initial consultations with E-Learn Design are free.