Hashtags are a popular, largely undocumented, and not well understood feature of Twitter. By using a hashtag, people can mark a series of tweets (updates) related to a single discussion or event. You’ll often see updates that include text preceded by the “#” character, like: #sxsw, in this case indicating tweets related to the South By Southwest conference. They’re called hashtags, because the # sign is often referred to as a “hash mark.”

A hashtag can be any character or characters you choose, but should be short (you have fewer than 140 characters in a tweet), memorable, and not already in widespread use.

Twemes is a really cool site for watching all of the latest hashtags to see what people are talking about (they even have a “Tweme Cloud” of popular hashtags), or just a single hashtag of interest.

Tonight for example, I noticed a lot of people using #GNO. I can see all tweets using this hashtag by going to http://www.twemes.com/gno (Note that you do not include the “#” character here.)

You can use Twemes to display in a blog sidebar or elsewhere all of the Twitter updates with any given hashtag. Like any ummanaged feed, there are risks with this. If I use hastags and Twemes to display tweets with the tag #Socialized, both “I love #Socialized” and “#Socialized sucks” would be displayed in my sidebar.

To get the code for this, I went to http://www.twemes.com/socialized If you do this, you will see several options. To get the code for a blog sidebar, click on “Widget.” You will see both an RSS feed for this hashtag, and below, the embed code for displaying all Twitter references to #Socialized in the blog’s sidebar. Just copy and paste the code. To get the code for any hashtag, just change the text after the final / in the URL above. You can see the results at the bottom of my sidebar.

You don’t have to use Twemes, but I like it. You can also use #hashtags.org. Just follow @hashtags on Twitter and #hashtags.org will index and display all your hashtags. (They autofollow so it’s quick.) Thanks to Rebecca Leaman for the pointer to #hashtags.org. #hashtags.org didn’t find my “socialized” tweet, but it may need some time to index my latest tweets, so I am going to try it again tomorrow.

Hashtags, Twemes and #hashtags.org are very useful for tracking Twitter conversations. Some Twitter clients and add-ons can also search for hashtags. I tried this tonight with Hahlo, my favorite Twitter iPhone client. Give it a try and let me know how it goes.

Tags: twitter, hashtags, twemes, sidebar, tutorial, hashtags.org