Take your pick: lakes, streams, hills, forests, trails, gardens, yards, home repairs (yikes!), roads, turf, sky diving or whatever it is that helps you get that bit of sunshine on your shoulders. Call it medicinal if you need an excuse - we all need vitamin D, right?
You can find summer (and winter) equipment for outdoors, like canoes, paddleboards, sailboats, backpacks, tents, etc. from BSU's Outdoor Program Center (OPC).
Nice Ride Bemidji offers flat fee by the hour, day or week for bicyles to anyone over 18, age 16-17 with a parent. These orange bikes are available at various locations, including the state park. If you have your own bike and it needs some simple fixing, check out the repair station in front of the public library.