More and more people are starting to use “hashtags” or “twemes” on Twitter. On Twitter, using a phone or an IM client, you can track a specific keyword and people are using these hashtags to track particular topics or facilitate communication within a group. This also allows for communication at a gathering, such as a conference, without having all the Tweeters follow one another. For example, people at SXSW will be adding #sxsw to their tweets. The hash convention was derived from IRC channels.
https://twemes.com is a convenient way to see tweets on popular topics.