You can track anywhere. JIRA is good. Google Docs works too. UserVoice if you want it public. Record customer contact information at all times so you can follow up.

The logout page is a good place to ask as well.

Most customers get frustrated when requests go into the trash can. It is important to show progress against requests. Simply referring to the request system in feature announcements is sufficient. "We had 18 requests for FizzBuzz. After talking further with customers, we designed..."