To me, Mingle is agile planning tool done right. Here is some of what I like:
- It does not target one specific method. It has a concept of project templates, where you can choose from three default ones: a default Agile one, a Scrum targeted one and an XP targeted one.
- If you choose to use, say a Scrum-focused template, you get views and naming, that matches scrum (sprints, backlog, ...)
- There is no mention of timeframes. Yes, you can plan cards in sprints or iterations, but there is no control of start or stop on specific dates.
- Cards are taggable, making it possible to group arbitrarily
- Cards have attributes (sprint number, business value, ...), which are easily edited and you can add both completely new attributes, but also new values for a given attribute.
- There is a brilliant planning/editing screen, which can switch between list or grid view.
- In grid view, you can drag and drop between the attribute you have chosen to group on. For instance between sprint numbers to do release planning, or between priority, if doing prioritization.
- In list view, you can select and edit attributes of multiple cards easily.
If this is not enough for you, you can always check out the cool stack it is running on. It is written in Ruby on the Rails framework, but is executed on the Java VM through the marvelous JRuby and served through Jetty. Of course, this has no real meaning to the end user. But I find it cool, and boy they must have had fun mingling.
Trust me, Mingle is worth looking at.