PIF,

Here's a link for s/n in Minnesota.

http://www.lovethatcat.com/spayneuter.html#mn

This link gives you a certificate/voucher that can be used at participating vets in their area:

http://www.spayusa.org/

Here's one more, although I'm not sure if it includes Minnesota. They can call to see if there are any programs in their area.

Hope this helps!!