Same story here - regular interest from corporate groups and a real struggle to find opportunities for them. Especially when they are looking for something for all 50 (or 100!) employees to do together on the same day. I don't have anything that 50+ people can do simultaneously. So in those cases it is more about educating the corporation about what our capacity is for group volunteers.
We do have groups of 10 -15 help with landscaping projects at our Sculpture Park location. Also having 10 or so people help with set up for fundraising events or a large outdoor winter light festival has worked in the past. For smaller groups (5-10) we have them help at the art activity stations at our Remix - a late night, 21+ event we host 3 times each year. We currently do not allow any temporary/one-day volunteers, including corporate volunteers, to assist at any event where children are in attendance, since we do not run background checks on those folks. Currently there are conversations happening about changing that rule for corporate volunteers, but it is still undecided at this point. If we do go forward with allowing it, I think we would have small corporate groups help at some of our family festivals and community opening events. We did try having small corporate groups (4 or so) folks help on busy free days with greeting and wayfinding, but in the end found that the volunteers were frustrated in getting asked soooo many questions that they didn't know the answers to, so it ended up not being very successful.
If someone has solved this corporate volunteer conundrum - speak up!
Jenny Woods
Assistant Manager of Volunteer Programs
Seattle Art Museum