Note: there are hundreds of distributions. These are just my favorites.
1. Ubuntu (cick here for official website)
-extremely easy to use, great for people who are not good with computers.
-very good start menu searching
-Doesn't support categorization of apps
-panel cant move, can only be on the left.
-project managed by Mark Shuttleworth
Now included by manufacturers in a few Dell, HP, and Lenovo devices.
2. Zorin OS (official website)
-very, very beautiful.
-Very easy to use
-supports app categorization
-looks like Windows 7
-Supports all Ubuntu applicatoins
-not a very wide variety of themes
-managed by Kyrill Zorin
-Only distro to have a "look changer" that completely changes the layout of the OS (so far)
3. Linux Mint (Official Website)
-Easy to use
-very stable OS
-supports Ubuntu applications
-not quite as easy to navigate as Ubuntu, but if you are comfortable with computers you'll be fine.
created on a community level, not by a single developer or by a company.