Shell enhancement to round-robin through list of directories

When working at the command line (Unix mostly) I am often working with files in several directories at once. The pushd and popd commands are useful but require a strict stacked directory use and require too much planning for me to use efficiently. (Clearly, self actualization has reached a new level of specificity.) What would be better would be a way to change directories by rotating through a list of directories. Much as is done today with applications vis Cmd-Tab under Mac OS X and Alt-Tab under Windows. Configuring the list of directories should be via a hot-key. The hot-key should work not only when in the current working directory but also when using filename completion. Often, the directories I want to return to are discovered during filename completion. So, one hot-key is used to add and remove directories from the list and another hot-key to change directories to the next directory in the list.

Re: What the iPad Means for the Future of Computing

Comment regards Wired's What the iPad Means for the Future of Computing:

What the iPhone did (and iPad will do) is to bring back sanity to interface design. For decades UI vendors — Microsoft, Apple, HP, Sun, etc — brought to tool/application front-end development well considered and consistent structural and visual interface elements. The tool’s new users needed only to learn how these elements were applied to the business function to use the tool. The value of this UI work was, some how, lost during the rise of the web.

The other element of the iPhone’s success is single user focus. The iPhone becomes the tool/application in use. User multi-tasking is not a requirement to productivity. Switcher was one of Apple’s greatest productivity successes. It was ahead of its time and ahead of the capabilities of the hardware. The hardware in the iPhone and the iPad make switching to another application fast and into the same context you were when you left.