Currently in Distrowatch's third spot in popularity, Linux Mint is an Ubuntu-based distro that was just launched in 2006. The operating system adds to Ubuntu with its own, distinct desktop theme and a different set of applications; also unique to the distro are a variety of graphical tools for enhanced usability, such as mintDesktop for configuring the desktop environment, mintInstall for easier software installation and mintMenu for easier navigation.
Mint enjoys a well-deserved reputation for ease of use, so it's another good one for beginning users. It also includes some proprietary multimedia codecs that are often absent from larger distributions, thereby enhancing its hardware compatibility. Mint doesn't have a fixed release schedule, but typically a new version comes out shortly after each stable Ubuntu release.