Whenever I think of podcasting an event, I always look around to see what big conferences and shows are happening around town. I live in a pretty big town so there's usually something to choose from. As it turns out, I've never actually podcasted a live event because I always scare myself out of it. However, one thing I have learned is that you don't have to pick the Mayor's Annual Ball to podcast. There are plenty of smaller events that would make interesting mobilecasts.
From a business perspective, a trip to the stock market might make a great soundseeing event. I don't know if they'll let you walk in there with a recording device, but if you have a little iRiver or something like that, they probably won't notice. Perhaps recording bits of a business-related conference or presentation and then offering your commentary on what was said?
There are lots of opportunties out there to turn a small or otherwise every-day event into a great mobilecast.