Altassian is cool, I like this company.

I regularly work with a  lot of their products, namely: Jira, Confluence, Fisheye, Crowd & CrowdID. I'd love to try Bamboo, & Crucible but I haven't had a need for it yet. I must admit that preparing a server for these applications may be daunting, especially if you want them to integrate into Tomcat, as opposed to running them standalone. The applications themselves are 110% rock solid.

Support from Atlassian is extraordinary and so if you have problems installing or configuring the software, they will help you and get it working. Their documentation is pretty comprehensive though and if you dig around their wikis and forums you should dig yourself out of most problems. I always run their applications in Linux, under Tomcat and so far they've worked great in Centos 5 and other similar flavors. Most of the complications I've had with them are actually related to getting Java working in the OS, and then getting Tomcat to behave. Their single sign on kicks serious ass. Where I work, we've successfully integrated WordPress, VBulletin, Jira, Confluence, Fisheye, a vTiger backend, and couple of custom Java apps into what is now our new corporate website. It works in such way that you only need one username and password to get to any of those applications --provided you have the right level of permissions. Register once, and you can log into wherever you need to log in, if you've purchased some extra level of access, then it automatically grants you access to that. It works great.

Directly from their website:

Atlassian is an Australian software company specialising in collaboration and development tools.

[Their] mission is to build a different kind of software company — one that listens to client needs, values innovation in development and solves customer problems with brilliant simplicity.

Check them out here.