Corned beef hash, hash browns, there are many great types of hash out there (don't start, I get it).  All too often overlooked by online marketers and webmasters, however, is the old school hash symbol (#), also known as the pound symbol.  This little beauty can do some pretty cool things for you.  It can control duplicate content problems, martial affiliate links, and even help you control the content shown to different visitors...not bad for the old shift+3. Watch the video to learn what a hash in the URL can do for you.

SEOmoz Whiteboard Friday - Using The Hash from Scott Willoughby on Vimeo.

Here's another article worth checking out on this subject; be sure to pay special attention to the section about URL fragments: URL Referrer Tracking. Also keep in mind that analytics will have to be set up to track the URL info after the hash, which Rand forgot to mention in the video - this can be accomplished using filters in services like Google Analytics, Omniture and Indextools, or with a bit of Javascript on the page.