One can even see the memory consumption and CPU usage of each tab and extension.
The latter displays total memory usage at the top of the page.
edit: As child poster noted, total memory is overcounted as it seems to be quite difficult to audit exactly what memory is shared within each child process. (see https://code.google.com/p/chromium/issues/detail?id=25454 )
One can even see the memory consumption and CPU usage of each tab and extension.