What is JIRA from Atlassian.com ?
JIRA is an interesting system (an Enterprise Form and Workflowsystem, must often called an Issue Tracker) - very stable and with a lot of expansion possibilities, and can be - with an onDemand instance be used for $10 a month.
An onDemand (cloud based) has some restrictions regarding plugins, as an alternative option, run the product on a "local" or cloud based server.
I can recommend the book here for JIRA Admins (and developers)
Labels List spaceKey ATLASSIAN