The flagship IAOA conference is the The International Conference on Formal Ontology in Information Systems (FOIS), held biannually.
Past FOIS events are listed in the FOIS series website - the FOIS 2014 conference will be held in Rio de Janeiro, September 22-26, 2014.
Other main IAOA events include the Interdisciplinary Summer Schools on Ontological Analysis and the IAOA Summer Institutes, held in an alternating manner.
The next IAOA summer school 2014 will be held in Vitória, Brazil, between September 15-19, directly preceding the FOIS conference. The IAOA summer school 2012 was held in Trento, Italy. The last IAOA Summer Institute 2013 was held in Fiesole (Firenze), Italy.
Further events include the Ontology Summits, the WoMO workshops, as well as the FOMI workshops - links to past and upcoming events can be found in the blog below.