Another URL question

[eluser]wintercounter[/eluser]
Sorry folks, i've tried to search the Forum and the Docs, there's probably an answer in the forum to my question, but I even don't know how to search for...

How can i make dynamic segment 1?
Like Wordpress does...
For ex: mysite.com/codeigniter2.0_has_been_relased
Instead of: mysite.com/entry/codeigniter2.0_has_been_relased

Of course, if there's no match, than it should search for other controllers like contact, about_us, etc...

Thanks for your help!