Just like using Alt+Tab for Windows except now for your browser tabs. Use Ctrl+Tab or Ctrl+Q or Ctrl+`(~) or assign your own shortcut key for swapping back and forth between your last viewed tabs.
3.0 (Jan 9th) - Check out the options page: I added the option to use Ctrl+Tab finally! 2.23 (Oct 15) - Renamed methods to chrome.runtime 2.22 (Oct 8) - Fixed issue caused by emtpy localStorage.tabs 2.21 (Jun 16) - Added a close link in popup 2.20 - Fixed issue with Chrome 28 and cached pages 2.19 - Fixed issues with CSP 2.18.1 - Fixed issue with always switching to first tab 2.17 - Using event page to save memory 2.15 - Fixed issue with unable to type in Google Docs 2.14 - Updated to manifest 2 2.11 - Changed colors 2.8 - Bug fix: Removed error in log 2.7 - Added option to show all open tabs in the 'max recent tabs to show' dropdown