Its very simple, but its saved me quite a bit of time when developing new themes. Basically this plugin will equalize the columns in your theme to ensure that they are of equal lengths.
NOTE: Your theme must use the following column names: "rightnav","bodycontent","leftnav","sidebar","sidebar1?,"sidebar2?,"content".
You can modify the equalcolumns.js Line 2 to contain any column definitions you may have for your theme
All the information (general, changelog, installation, upgrade, usage) you need about this plugin can be found here:
WP-Equal-columns Readme.
NOTE: I did not write the js script. I would give credit to whoever wrote it, but it doesn't contain any author information. If you wrote this js, then contact me, I will add your credits here.