Mists of Stone Forest Grove- formerly a Keltrian grove, this is probably the oldest and largest Druid group in MN that's still running. I've been to some of their rituals and they're good folks.
Location: Twin Cities, run by Phil Hutchens
Geal Darach Seed Grove- this is a recently formed OBOD (Order of Bards, Ovates and Druids) grove.
Location: Twin Cities
Contact: Alferian, Geal-Darach Chief Druid at email@example.com
I know this guy, he seems nice, and he also runs the Avalon College of Druidry.
Invisible Druid Order- I don't know anyone in this group.
Sacred Celtic Order of Balance- Celtic Pagan group I found on Witchvox. Looks like more of a Wiccan slant, I don't know anyone in it.
Location: Sartell, run by Lady Sherrell
Old Belief Society/ Tuath Seancreidimh- Celtic Recon/Traditionalist- run by Andrew Jacob.
Folks, feel free to anything I've missed or any info on these that you're aware of.