WeFollow: Though the founder of this is Kevin Rose and there is Digg behind it, you and others on twitter help create this directory. It is quite simple in fact. Just add by tweeting @wefollow and three #hashtags. The hashtags will give scope for description.
This is pretty simple and I will be using it more regularly.
Just Tweet It: like WeFollow and Twellow, JustTweetIt is another user generated directory. It is a bit more complicated than the above mentioned. However because it has so many profiles, this is not a tool to ignore when you are interested in searching for people.
Haven’t found a use for this one yet but can’t hurt to keep track of it.
Twubble: Twubble follows the “chain” strategy. It believes that if you are following a Mr. A and he in turn is following Mr B, Ms C and Ms D, you’d be interested in Mr. B, Ms.C, etc. Not a bad tool or concept, especially if you believe in the theory of “a friend of a friend is a friend”
I personally think this is pretty creative and it gives us good options of people we may wish to follow.
Twitterel: What if the name search or location search or common interests don’t get you the people you are looking for? There’s another option – keyword search. This directory generates results for specific keywords. Like google alerts, it keeps sending alerts via mail or @reply, whenever it comes across the keywords in tweets.
Simple to use and interesting but can give you a lot of alerts that are not relevant to your need.