In case you don't know what ZFS is (and want to find out), then there's a presentation at London OpenSolaris User Group on the 16th May, from 18:00 at Sun Microsystems. And if that's not enough, nibbles and drinks are provided :-)
Jarod will present "ZFS: Under The Hood", which aims to lift up the ZFS Bonnet and explain the building blocks of the ZFS engine. Without getting too bogged down with specific implementation details, he will cover the technical function of all the key components such as the ZPL, the DMU, and the SPA. Jarod says "You could think of this as a "ZFS Internals Lite".
You should send a mail to Sean Sprague losug_att (at cvok dot co dot uk) if you're interested in attending.