McCredie Hot Springs is a rustic soak in the Willamette National Forest, about fifty miles southeast of Eugene along Highway 58. The springs sit by Salt Creek, with simple access from the day-use area rather than the developed-pool setup you find at commercial hot springs.
That lack of polish is the point, but it also means you need to behave well. Pack out everything, expect variable pool conditions, and be aware that clothing norms can be loose at natural hot springs. It is an easy stop on the way to Oakridge or the Cascades, especially in cool weather.