I consider the jQuery plugin "jQuery resize event" to be the best solution for this as it takes care of throttling the event so that it works the same across all browsers. It's similar to Andrews answer but better since you can hook the resize event to specific elements/selectors as well as the entire window. It opens up new possibilities to write clean code.
The plugin is available here
There are performance issues if you add a lot of listeners, but for most usage cases it's perfect.