My personal preference is for "Lunch and Learn" format - as both a learning and sharing opportunity as well as a celebration. These get-togethers are professionally stimulating and a special treat to spend time with others in a collegial setting.
I'm having to retreat somewhat. We started off with Technology Enhanced Instruction which was shelved due to layoffs and retirements. I had the opportunity to restart several years later. I thought we needed an fresh coat of paint. The old title was so "yesterday" so we switched to calling it Technology Supported Learning and offered it as a credit course. And nothing happened. This just didn't get anyone excited.
So back we go - informal learning, Lunch and Learn format, celebrate getting together with professional colleagues and talking about Teaching, Learning and Technology.