Lately, everywhere I've read or seen, there are workshops being held. It made me wonder if the term is a candidate for over abuse syndrome?
There are other types of people gatherings that might be more applicable depending on what you're hoping to achieve:
Meeting - people discussing a topic of shared interest, often to achieve a common goal, sometimes formal with actions.
Roundtable - peers offering free and frank discussion around a topic, maybe with no tangible outcome
Forum - people learning and sharing ideas - maybe speakers presenting
Summit - peer to peer senior people soapboxing big issues
War Room - people with diverse interests brought together to solve a problem
Brown paper bag meeting - there's supposed to be something racy about these, they work best when time is short and the topic can be condensed - maybe for thought leadership presentations, generation of new ideas, scheming...
Most formal of all in my mind is the workshop - a facilitated meeting with a structured outline intended to produce results.