Well for the newbie you can try mandrake or red hat. However, for the power user I would recommend slackware, or my friends would recommend gentoo or debian. I have not tried debian or gentoo however I have heard good things. Slackware is my favorite becasue it is not bloated with extra crap, does not use rpm, it is powerful and secure, and it is very unix like. Slackware is also one of the oldest linux distros out there, its tried and true, it kicks royal ass!