Twitscoop

Twitscoop is a Twitter tool that tracks trends, there is a real time consolidation of topics that takes place in the form of a tag cloud on the right-hand side, which is constantly updating (unless you pause it).

You can also tweet from the tool, as well as search. Twitscoop's claim to fame is that you don't have to reload your page, updates are automatic.

WeFollow - tag yourself by interests

WeFollow is a very simple tools that allows users to submit their own tags by sending a tweet to WeFollow. It uses these tags to help users find other people based on the topics they tweet about the most. The WeFollow site serves as a ranking and search service that allows users to find other followers based on their interests or location.

Just click on the "+Add yourself to WeFollow." You can choose three tags - which describe you and your interests. Then the info is sent and added to their listing (and added as a tweet of Twitter as well.

You can change your tags when you interests change. You can search out people with a particular tag and you can see how they (and you) rank for that tag. It is also a good way to see trends.

Hashtags

This one scares people, but in reality it is really easy. There is only one main rule, which can be said for most anything on Twitter - don't over use it!

This is simply any topic with a hash (#) in front of it. Why? So that people can (1) spread information and (2) categorize themselves or their conversations, making it easy to search and find other conversations on the same topic. For really hot topics, you can usually find them in the top ten searches trends in the right hand side of your Twitter home. Here is one from June 15th:

One of the most popular ones (to date) is #followfriday. And also anytime there is a social media conference you can be sure there will be a hash tag. In fact, following people who are at a conference is almost as good as being there. People keep you up minute-by-minute of what is going on!

One last thing to note. If you want to creat a hash tag you should first find out if it isn't already being used. Search first, then post - Go to http://hashtags.org/ and search for existing hashtags in use.

If it is already in use you can leverage conversations that are already ongoing around your desired topic. And if you're interesting, they will follow you.

For more information, there is a really great article from Mashable on this.