I agree that Fedora, Ubuntu and Mint are all good for starters. Ubuntu is probably the distro most users are starting on these days, so there are a lot of websites where you can get help with it and find tutorials. Most of them actually apply to any linux distro, but there are some differences between the distros. One thing that is different is the package manager. Fedora uses yum, and Ubuntu uses apt. You will see very few differences on the command line.