I'm a fan of Trello. I signed up on launch day when Joel presented at TechCrunch. I backed into Kanban, and I've had an opportunity to consult and introduce teams to agile practices.

Sticky notes are unironically an important part of the job, but a small part. And when freeform ideation is needed, then stickies and other movable objects can be helpful in communicating a space and sometimes revealing subtle (or not-so subtle) biases or boundaries within a concept space.

In Trello, work generally moves column to column; from left to right.

Work can be prioritized relatively by the ordering of cards on a list.

Yet, some task cards convey more dimensionality. For example: user value, effort.

These dimensions can be translated into axes.

Thus, it is possible to use the Trello API to display all the cards, then drag them x, y into space as another way to interact with your data.