StaticTyping of the (side)effects of a method.
Java's CheckedException is an example of an explicit effect type.
Chapter 3 of "Advanced Topics in Types and Programming Languages" Benjamin C. Pierce has a nice formal introduction with application to Regions. Available on Google here:
http://books.google.de/books?hl=de&lr=&id=A5ic1MPTvVsC&oi=fnd&pg=PA87&dq=effect-typing+method&ots=PmoEkJcy5w&sig=QylSEShgA4jypQ6jnNEOdZNP_dQ
Related to OnMonads (monads and effect types seem to be dual or at least strongly connected)