There’s Fedora, Mandriva, SlackWare, OpenSuse, Gentoo, Ubuntu, PCLinuxOS and many others. The distro’s I just labeled are some of the top rated (most used). I personally use Mandriva Linux 2008.1
I thoroughly recommend Linux Mint 6 Main Edition which is Ubuntu based. Its easy to install and easy to use plus it comes with much of the software you are likely to need preinstalled.
You would be best off RUNNING IT LIVE so you can get the feel of things.
Linux Mint 6 Release notes
Linux Mint 6 Download
Once you have got the feel of things you may wish to consider an installation
The Perfect Desktop – Linux Mint 6 (Felicia)
You download the ISO. image of Linux Mint 6 then you need to create a Bootable CD from the ISO. This can easily be done using Nero Burning ROM or similar software. Linux Mint can also be run straight from the LiveCD you have created without touching your Hard Drive.
Remember you can RUN IT LIVE !
Currently running Linux Mint 6 ext3 with Compiz 0.7.0
Mac OS X isn’t Linux. OS X is built on FreeBSD (Unix) and on top of that is it’s own operating system in general because of how it’s setup and operates. All Linux distro’s offer free open source operating systems and they’re all free. There really is no “best distro” for Linux. There are over 100 distro’s for Linux out there. Just a matter of finding the one you like most. There’s Fedora, Mandriva, SlackWare, OpenSuse, Gentoo, Ubuntu, PCLinuxOS and many others. The distro’s I just labeled are some of the top rated (most used). I personally use Mandriva Linux 2008.1 because it works well with my dual monitors.