Solid of them to do that, but FogBugz is terrible. Our dev team found it to be tedious (4 developers).
We've switched to Pivotal Tracker (also in free beta) and find it much more suited to rapid development and "agile" practices. In particular, we find the predictive tools actually useful.
If you like Jira you might not like the simplicity and clean UI of FogBugz. We switched from FogBugz to Jira at my last job and I personally didn't like it very much. But management liked the flexible reporting and complicated workflows they could invent.
Personally I think Jira looks like it was written 10 years ago and can get quite slow at times, which together with the fact that there's no AJAX and every click reloads an entire page means it can be a very unpleasant experience.
I haven't gotten to use FogBugz so I can't compare the use of the UIs. AJAX would be really nice, although I haven't had any performance issues. We replaced Mantis and Bugzilla with Jira at one place I was at, and it was significantly faster than either of them.
I'm in love with the ability to very easily create different issue types with different attributes, states, and work flows. That lets us use the same system as a project management tool with release schedules, features, sub-tasks, reporting on hours breakdown by resource etc..., and a customer facing issue reporting/tracking system, and an internal bug tracker, etc...
edit---
Also love the great integrations with Confluence, Eclipse, SVN, Hudson, etc....
I just started using Zoho Project. I am fairly impressed with the task dependency, milestones, team integration and such. You can also embed files or edit within with integrated zoho writer, ppt, calendar, alerts.
It is free for one project and unlimited users, paid ones have more space and projects starting at 12$/mo
We've switched to Pivotal Tracker (also in free beta) and find it much more suited to rapid development and "agile" practices. In particular, we find the predictive tools actually useful.