Twitter is very easy to setup, and Twitter imports contacts from your email but none of my Gmail contacts are on Twiter :( so I had to added some "suggested users." At first I wasn't really sure what the purpose of Twitter was, but this changed after some exploring. Twitter lets the world know what your doing and lets you know what the world is doing, this is done via updates where you can type up to 140 characters into a facebook-like status box. If the updates are not protected, anyone in the world can follow them, I think this is so cool. I am following updates from people such as Levar Burton, Lance Armstrong, and Al Gore. It sort of gives a feeling of connection to these people whom I'll probably never meet in person in my life. This is how Twitter is so much different than Facebook where your connected to smaller networks. Google has signed up to Twitter, and rumors have it that they may in fact purchase Twitter.
Another part of Twitter that I discovered yesterday is that you can post an update for blog posts via Twitter Feed. This is extremely easy to setup, all you need is an OpenID account, and within a few clicks, your blog updates are sent directly to Twitter as status updates which should increase blog traffic a lot.
A major aspect of Twitter is the mobile side. First of all, the mobile site is very cellphone friendly, graphics look excellent and it is very easy to navigate. Second of all, Twitter can send SMS text alerts of updates from followers, note that if your in Canada, it only works on the Bell network. Users can also update their status via text.
Since yesterday, I've been using Twitter alot. I think this is going to get really big, people want to know what the World is doing!!