LAMMPS workshops have been held in Albuquerque, NM, roughly every 2 years, usually in the summer. The programs, presentation slides, and posters for each workshop can be accessed via the following links. Each workshop included a tutorial session with slides that can also be downloaded.
A workshop-like tutorial and symposium, entitled Materials modeling with LAMMPS was held in August 2016 at Temple University.
Also see the Tutorials page page for additional info on past LAMMPS tutorials, with lots of downloadable material.