Deskzilla is a desktop client for Bugzilla which is Mozilla's bug tracking software for developers.
Deskzilla makes tracking bugs easier courtesy of a hierarchy of filters that gives the user an instant overview of your project. The handy thing is that Deskzilla allows you to enter and track bugs offline as well as online, making it ideal for when your Bugzilla server is not available for some reason. Deskzilla also makes carrying out commands and functions within Bugzilla a litle quicker and more accessible.
Deskzilla can be a little clunky because it's written in Java but the good thing is that because of that there's no additional server installation to do. There's no doubt that using Deskzilla makes things a lot quicker than having to switch to Bugzilla every time you want to add or track a bug. Note as well that it's only free for use with open source projects.
If you use Bugzilla regularly and need an on and offline way of bug tracking, Deskzilla may be just what you're looking for.