Wall-crossing for Donaldson-Thomas invariants, Oxford, September 2017 (beamer slides).

Stability conditions and quivers, Stavanger, September 2015 (beamer slides).

Stability conditions and wall-crossing: Three talks at the AMS algebraic geometry festival in July 2015: video, beamer slides 1 2 3.

Lecture notes for an introductory course on derived categories of coherent sheaves, Warwick, September 2014.

If you want to learn about stability conditions, start by watching Daniel Huybrechts' talks at the Issac Newton Institute.

Three talks on stability conditions from 2013: the first two are introductory, the last is about a class of examples relating to moduli spaces of quadratic differentials 1 2 3.
Four lectures on Stability and wall-crossing from April 2012.

A video of an introductory lecture on Derived categories in algebraic geometry from March 2007.