Hashtags are a way of tagging things when you have only 143 characters to work with. In a nutshell, placing a hash mark '#' before a string hashtags it. Use the pklus sign '+' for spaces. The resulting 'hashtag' points to the hashtag website, which in turn has a link for each hashtag, where recent tweets posted to Twitter using that hashtag are listed. Here's the hashtag for #Jeff+Jarvis, here's the #Stephen+Downes (which will be a server error until somebody actually tags me; how's that for an inelegant depreciation?). It's a neat idea; I wish there were some way to work with this that wasn't site-specific. Via Amy Gahran.