While installing Ubuntu once more on a friends machine, I thought of the interactive progress bar element for wizard-type applications. Basically, it should provide very fast intuitive way for the person:
* to get an idea on how far he/she is in the step-wise process of some sort
* fast switch to particular relevant step (like go back few steps to change a name)
* ...

I may sketch it as follows:
[<] [++S1++][++S2 ][ S3 ][ S4 ][ S5 ] [>]

In the middle there is a progress bar like element, which is composed of click-able areas with short description plus a possible mouse-over or similar pop-ups with a more elaborate description, so that a person may really go back a few steps in one click to change some relevant information or do/redo actions on a particular step a while back. On a sides - some advance to previous/next step controls.

In the example above the person is on a current step S2, further steps like S3 S4 S5 might be inactive, while activation of active elements follows some logic.

Next, next step:
[<] [++S1++][++S2++][++S3++][++S4 ] [ S5 ] [>]

Sometimes, you realize, that you might have given not entirely correct response a while back. Here, going with a mouse over the progress bar and reading concise descriptions (if short step names is not enough) person may be able to go back exactly to required step without multiple use of go-back control element.

In my opinion such a control or set of controls (I do not know how complex will it be to implement something like this) might be very handy, since user may very fast recognize how far he is in the process using just graphical feedback to get an estimate instead of realizing what actually step 3 out of 7 means, and additionally go back few steps at once.

Hope, that I made the description and intention clear.