If you have used Twitter for any amount of time, you probably have seen odd hash mark characters show up on your screen. I always wondered what those were, and thanks to Nowsourcing.com (a fabulous site by the way, check it out) I now know!

Hash Tags are an easy way of adding a keyword to a topic or directing a comment to a group of people rather than an individual. It is pretty simple, actually.

Say I want to start a conversation around a particular topic, and I want to invite people to respond but I don’t want to limit it necessarily to people that I follow (or that follow me). I can add a hash tag.

For example, lets say I want to keep track of all the twittering around a conference - the people who are attending, the pictures they took, the conversations they are having, all in real time.

Hash Tags.org keeps track of hash tagged conversations. You can search for any keyword and see not only the most recent tweets that have been tagged, but also imagery and trending statistics.

Clicking on a user name will bring you to their Twitter page where you can opt to follow or simply look to see what else they might be talking about.

Nowsourcing uses hash tags to generate content for their site. Check out this “Overheard on Twitter” post for examples of using hash tagging as a means of mining conversational data.

Jeremiah over at Web Strategist has written a post about his essential Twitter tools, in which Hash Tags are mentioned. A good read as well!