Several parks that are currently hiring include:

Belle Isle State Park
Dodge #4 State Park
Fort Wilkins State Park
Hartwick State Park
Ludington State Park
Mackinac Island Harbor
Mitchell State Park
Muskegon State Park
Otsego Lake State Park
Outdoor Adventure Center
Petoskey State Park
P.H. Hoeft State Park
Proud Lake Recreation Area
Straits State Harbor

If you want to apply you can GO HERE, and click on "seasonal positions at state parks and harbors"