I have attended several kayak clean-up activities with Four Mile Run Conservatory Foundation and have found them to be exceptionally well organized. I am both a volunteer and a donor and anticipate that I will continue both for the foreseeable future.
Kurt does a great job communicating with volunteers about what to expect. They provide the kayaks, trash grabbers, safety vests, gloves, etc. Perhaps my favorite part, they have developed an innovative system mounting laundry baskets with bungie cords to their kayaks to collect the trash. It's easy and fun and a great way to spend a Sunday morning.
I have volunteered with other similar organizations previously and have found this one to be the most organized by far.
They go out of their way to make new and returning volunteers feel welcome and appreciated. A++. 5 stars.