Enter about:memory into the Omni bar (the address bar) and Google Chrome will display a nice summary of your memory useage and all Google Chrome-related processes. As a bonus, the summary section also displays the memory usage information for all other open browsers giving you a nice comparison!
Here is a list of other “about:” commands that provide interesting information and do some interesting things:
about:cache
about:crash
about:dns
about:hang
about:histograms
about:internets
about:memory
about:network
about:plugins
about:stats
about:version
Most of these can also be easily bookmarked by clicking the Star in the Omni bar.