My Five Favorite Not-Usual Linux Distros
Red Hat, Arch LinuxYes, "my bestest distros!" is a overworked topic, but it's fun and Ubuntu is not on this list. So perhaps this will introduce you to something new and interesting.
Red HatI like Red Hat both as a company and as a Linux distribution. They're a real Free/open source company, not a fake one trying to cash in because "open source" is cool, or wrapping a smidgen of FOSS code 'round with proprietary guff. Red Hat Enterprise Linux is rock-solid, with options for virtualization and a good middleware stack. Red Hat downplays it, but they also have a desktop Linux designed for the enterprise. The Linux desktop has always been a natural for the enterprise because of its built-in central management features, customizability, and stability.
Red Hat charges a stiff price for support, but unlike a proprietary software vendor you have options. For example you can pay the RH price tag for important servers, and deploy one of its no-cost clones (CentOS, ClearOS, Scientific Linux, etc.) on other machines. These are also great for learning and testing RHEL before taking the money-spending plunge.