I just discovered the YouTube channel of ICTP, i.e. Abdus Salam's International Center for Theoretical Physics in Trieste, Italy.
During the last month or so, they have posted a number of recent lectures (November 2010) by the winners of the Dirac Medal that they have distributed every August since 1985.
A significant fraction of the Dirac Medal winners are string theorists and I have chosen a sequence of 30-minute lectures by Joseph Polchinski (2008), Cumrun Vafa (2008), Michael Green (1989), John Schwarz (1989): two hours in total.
Note that Polchinski is being introduced by a young East Asian female physicist. Most other folks who introduce the speaker are much closer to the Muslim world, as appropriate for a center founded by Abdus Salam who was Pakistani.
Joe Polchinski talked about holography and unification. Cumrun Vafa chose to clarify the physical role of compact extra dimensions. Michael Green looks at string theory as a UV-finite extension of supergravity and he explains why SUGRA isn't enough. John Schwarz focused on superconformal field theories and their role in string/M-theory.
I also recommend to you talks by Roman Jackiw, Helen Quinn, John Iliopoulos, Jogesh Pati, Giorgio Parisi, David Gross (it has probably been shown on TRF), Shiraz Minwalla, Sergio Ferrara, Stephen Adler, and others.