I am interested in finding a site/sites that will give me access to a
broad range of lectures that are downloadable in mp3 format; lectures
that cover a broad range of academic subjects ( the public lecture
programme of a university/think tank/charity/specialist institution is
likely to include the sort of range and topics that i would be
interested in hearing). I have
found some good sites like
http://forum.wgbh.org/wgbh/forum.php?lecture_id=165 ( but even this
site doesnt have many of its lectures in mp3). Many Universities have
public lectures but few seem to have made them available in mp3. Is
there a site that brings together the available material? The reason
for the request is that i do alot of traveling and would like to
listen to the material on my I Pod ( If there were other means of
listening to lectures on the move i would be interested to know)

Check out audible.com.  It doesn't sound like exactly what you're
looking for, but you may find some suff there.  They have a speeches
and lectures category.