Elastic layouts are those where the whole layout scales proportionally as the user resizes the text in their browser. They are slightly different from fluid layouts which also display a similar degree of flexibililty: fluid layouts tend to occupy the whole of the window with elements resizing proportionally within the frame, whereas elastic designs tend to occupy a space smaller than what is available and the whole thing 'zooms' up.
As such, I felt the links Mike provided on the Zoom Layouts post actually were more appropriate here. So here they are. As before, feel free to suggest any others you might know of.