Many Open Source projects host their repositories with Google Code, where anyone can download the source. Now their bugs and feature requests can be just as open, with the read/write IssueTracker API.
You can search and retrieve issues, as well as the comments associated with each entry. In other words, you can make a completely new interface to browse the projects. Perhaps you want to add some meta-data, or apply a point system to encourage community members to claim or fix bugs.
Where the API gets especially powerful is through its ability to write to IssueTracker. Creating new issues programmatically means that bug reporting could be easily built into products or websites. Issues can also be modified, deleted and commented upon from the API (for more technical details see our IssueTracker API profile).