I speaking tomorrow at a internal Microsoft event. I've spoken at tons of conferences (PDC, TechEd, etc.) and for groups ranging form 1 to 2000. Today I did the rehearsal for one of the demos i'm going and it didn't really work... I had tomorrow blocked off to run through all the presentations to make sure i'm ready, but sometimes its good to get a little slap in the face to remind me to prepare adequatly... it's easy to get a little cavalier about these things...
Scott made a good posting about presentations also...