Free Bug Tracker/Issue Trackers tools

Take a look at Michael Flanakin's comparison of Web-Based Issue Trackers next time you need a free Bug Tracking/Issue Tracking tool and pick the one with the features you need. (Thanks Corey Trager)

And if you need one for a quick non-confidential personal project, there are also some hosted online for free to choose from -

Defectr, Unlimited Accounts
AceProject Basic
LightHOUSE Free edition, 1 project with 10 users
Issue Tracking Anywhere, supports up to 3 users
BugHost Lite, supports up to 3 users

SourceForge.net and CodePlex are popular open source project hosting websites that also provide supporting features like source control, discussion forums and issue tracking.

Related link:
Rating the quality of a software team