What types of exercises are okay for stress fractures?

Non-weight bearing. Stress fracture are considered overuse injuries. In order to heal they need rest. This does not mean you have to stop everything. You do have to stop activities that aggravate the area involved. Most of the time you can find some substitute activity. The key is that you feel no discomfort while performing the activity (note: i said "discomfort", not "pain"). E.G: swim instead of run.