Friends of Virgin Islands National Park has many events, from full moon hikes, bat netting, meditation and yoga at Peace Hill, guided walks, all sorts of experiences.
Get Trashed St. John is an organization that meets and picks up litter, they have a Facebook page to see if anything is planned during your visit.
St. John VI Pottery (aka Pottery in Paradise) is near Pickles in Paradise in Coral Bay. They have a shop where the artists sell their work, but they also provide an opportunity for open studio time, and sometimes classes/workshops. stjohnvipottery.com
Scuba, if you are familiar, great! If not, St. John is a fantastic place to test the waters with many shallow but interesting dives. Low Key offers discover scuba, open water certification, night dives, and if your lucky a trip to French Cap ;) Low Key Watersports
C.O.R.E. stands for Caribbean Oceanic Restoration & Education Foundation. Among other marine programs it serves as the Lionfish Response Program. If you should see a lionfish in your snorkels or dives please call the sighting hotline: 340-201-2342 -OR- visit corevi.org
Guided kayaking, paddle boarding, and hiking adventures throughout St. John. usviexpeditions.com