I've given several workshops and skillshares about the ideas behind
OpenPGP and how to use gpg and its various frontends to
small-to-medium groups (5 to 25 people).

I led an effective skillshare on the nature of X.509-based
certifications and how they are used in SSL and TLS back in 2003 or
2004.

I co-led a surprisingly large (~>50 people? packed room!) discussion
about free software and why it should matter to users as well as
developers a the Grassroots Media Conference a few years ago with
Alfredo Lopez and Laura Quilter.  This was a very active discussion,
and topics ranged from motivation and policy to moderately technical
concerns.

I presented a poster with a colleague on a novel acoustic correlation
method at ICASSP (the IEEE's International Conference on Acoustics,
Speech, and Signal Processing) 2001 (though i've recently let my IEEE
membership lapse).

I've introduced numerous people to the monkeysphere via IRC
discussions, and have a strong handle on both:

 * the necessary details to keep a technical audience engaged

 * the bigger-picture goals to keep a non-technical audience engaged