1. Linux Mint (Ubuntu Based): This OS is freaking fantastic. Extremely easy for Windows users to adapt to, and comes with lots of bells and whistles. And yet, it uses very little resources and is very simple to use. This is the only Linux distro that I would buy if they charged money for it. But they don't, so yippy!
Default desktop: Gnome
http://linuxmint.com/
2. Slax (Slackware Based): I love this little OS. It's designed to fit on a pen/flash drive (the entire OS is only 50mb in size), and yet it comes with everything you need. Great!
But, there is a catch. It will be difficult for new people to use, as you have to set up a lot of stuff the old fashioned way (manually). So newbies beware!
Default desktop: KDE
http://www.slax.org/
3. Ubuntu (Debian Based): Nice, simple, stable. Three words that describe this great OS. Ubuntu is extremely easy for people that are new to Linux to adapt to, and has active forums for support if you need help. It's website is also very well documented, providing tutorials and troubleshooting guides. If you're new to Linux, I recommend using this, or Linux Mint, hands down.
Default desktop: Gnome
http://www.ubuntu.com/
4. Mandriva (parent OS): Mandriva was pretty much the first Linux distro that was designed with ease of use in mind. Extremely polished looking by default, it is sure to grab your attention.
Default desktop: KDE
http://mandriva.com/
5. Ubuntu Studio (Debian Based): If you create/edit videos, photos, video games, music, or just like having that option out of the box, then this is the OS for you. It comes pre-installed with over 100 different applications that will assist you in creating anything multimedia. I use it all the time for music creation, and I love it.
Default desktop: Gnome
http://ubuntustudio.org/
*Special Mention**
PC-BSD (BSD Based): Although it's not a Linux OS, it is based on BSD, which is related to Linux (MACs are based on Darwin, which is a BSD kernel) . Both spawned from UNIX, so they're siblings. This is an up and coming OS that is very easy to use. It comes pre-installed with a bunch of video codecs, can play DVD's out of the box, as well as almost anything you need to in your web browser. There are a few bugs, however, but no OS is perfect. Keep your eye on this one. I anticipate that it will be widely used within the next year or 2 (and by widely used, I mean on the level that Ubuntu is now).
Default desktop: KDE
http://www.pcbsd.org/
So there you have it. My favorite distros! Keep in mind, I have used over 100 alternative operating systems, so I had to think long and hard about which ones I liked the most. Except for Linux Mint. That was an easy #1
