Oxford's podcast of the Isaiah Berlin Centenary (Oxford on iTunesU, iTunes feed, site) contains one lecture about Berlin and several lectures by Berlin himself, recorded in the the 1950's.
One of the lectures is on a Russian writer, Alexander Herzen, about whom I had never heard, I must admit. Berlin turns out to be a great admirer of Herzen and his lecture on the writer is very fascinating. The importance of Herzen is not necessarily as a writer, although Berlin praises his autobiography as one of the great works in Russian literature. Herzen's meaning lies in his vocation as a publicist and political thinker.
Herzen was, according to Berlin, the first to found a liberal newspaper in Russia and as such a pioneer of free press and free speech. This put him in the position to politically choose between the Russian traditional order, the liberalists and the socialists. Herzen swayed back and forth but between liberals and socialists he kept sitting on the fence. And if this is vieed by some as weakness, Berlin praises this as a strength, just as he finds this a strength in the novelist Turgenev. In Turgenev's Fathers and Sons a similar quality is displayed. That is subject for yet another lecture.
More Isaiah Berlin:
Isaiah Berlin on Philosopher's Zone and Oxford,
Moses Hess according to Isaiah Berlin.