Today, Mark and Jon finally shipped ShellRunAs, a Sysinternals free tool that adds a "Run as Different User" option to the right-click context menu.
The command-line Runas utility is handy for launching programs under different accounts, but it’s not convenient if you’re a heavy Explorer user. ShellRunas provides functionality similar to that of Runas to launch programs as a different user via a convenient shell context-menu entry.
ShellRunas works on Windows XP, Windows Server 2003, Windows Vista, and Windows Server 2008.
This has been a HUGE request from IT Pros, so please enjoy!