Push F12 then you can right click on refresh and select 'Empty Cache and Hard Reload'
Edit 02/04/2013 to include everything
The documentation says Ctrl+F5 or Ctrl+Shift+F5
Reloads your current page, ignoring cached content.
Although some have reported this works, others have said it does not work correctly
Your other options are:
To open the Console tab, do one of the following:
Use the keyboard shortcut Command - Option - J (Mac) or Control -Shift -J (Windows/Linux).
F12 doesn't appear to be mentioned here but will open this console as well.
Chrome Developer Tools
2) Another interesting option is to open a new incognito window (Ctrl+Shift+N). This window won't use any stored cookies, cached content, or DNS resolutions, so you can test stuff in it without slowing your normal browsing down by dumping the cache. This is what I almost always do instead of clearing the cache.
3) Open Chrome Developer Tools (F12). Click the settings icon (a gear in the bottom right corner). Check "Disable cache". Now when you browse with your Developer tools open caching is disabled.
4) Finally there is also the option of the Click&Clean extension