Feeling the urge to procrastinate today? Hey, it's Friday, and Bethesda and id Software have come up with a perfect time waster. To celebrate the 20th anniversary of Wolfenstein 3D's release, they've put up a full-featured browser port of the game, which includes all of the original levels and assets from the PC version. You can find it at http://wolfenstein.bethsoft.com/.
The controls are pretty simple: arrow keys to move, X to shoot, Z to strafe, and space to open doors and secrets. You'll need a reasonably recent web browser to play, though, since it looks like the port uses HTML5. According to the "Read this!" section in the main menu, Chrome 16, Internet Explorer 9, Firefox 11, and Safari 5 are all supported.
If you can stand further procrastination, then you'll want to check out the accompanying Director's Commentary video. (See above.) In it, John Carmack rambles on about the game's history and various technical details for nearly 25 minutes. The first half of the video is all still images, but in the second half, Carmack actually plays through the first few missions while giving live commentary. It's a fun listen, though admittedly not the most productive use of one's time.