Creative Commons License Generator: Service allowing quick and easy selection of one of a range of Open Content licenses to meet a content creators' requirements (concerning attribution, whether commercial use is allowed, and whether modification is allowed).
Free Art License: Copyleft license applied to artistic content and projects.
GNU Free Documentation License: A version of the GPL for reference material.
kuro5hin.org: Creative Commons -NC Licenses Considered Harmful: "One particular licensing option...is a growing problem for the free content community. It is the allow non-commercial use only (-NC) option. The 'non-commercial use only' variants of the Creative Commons licenses are non-free, and in some ways worse than traditional copyright law -- because it can be harder to move away from them once people have made the choice."
October Open Game License: OOGL. The purpose of this License is to make a rulebook, game manual, sourcebook, supplement, or other written role-playing game document "free" in the sense that everyone is permitted to copy and redistribute it, with or without modifying it, either commercially or noncommercially.
Open Content License: License for the Open Content Project
Open Directory Project License: The license agreement for replicating ODP data.
Open Game License: License of the Open Gaming Foundation, as drafted by Wizards of the Coast.