Twitter has grown dramatically in the last year, so their servers are sometimes out of capacities when something important happens, and everybody tweets about it. Due to this aggressive increase of users, many programs appeared which can allow you to connect to Twitter in other ways than via "Web" method, providing you different ways to use Twitter, and many options to make it more efficient.
Yahoo!'s "Meme", a kind of Twitter, was launched by Yahoo! but so far, it has no success. I'm just thinking about how much time can Google resist without buying Twitter, because the more they wait, the more they will have to pay for it. And even if Google didn't declare anything about a possible acquisition of Twitter, many experts said that now is the moment when Google should take Twitter.
So, if you didn't do it already, I invite you on http://twitter.com/ to create an account, and then to start following me. My username is "ITeer". Enjoy Twitter !