The University Channel (UChannel)
The UChannel describes itself as "A collection of public affairs lectures, panels and events from academic institutions all over the world -- for you to view, listen to, stream or download." It began with a focus on public and international affairs, and has gone on to other subjects. 
Legal subjects (141 so far have been tagged as legal) include human rights, intellectual property, the brain and the law, teaching evolution in public schools, and guns in America.
Available in various formats, streaming - usually RealPlayer and Windows Media Player - and  downloadable .mp3 and .mp4, various lengths, usually at least 1h, no transcripts.