Where can I find a list of active mining claims in my area (Northern Nevada)?
You may want to check this out ESRI open data http://opendata.arcgis.com/ if this is what you were looking for.

One another thing is that you might want to contact BLM's Nevada State Office.

http://www.blm.gov/nv/st/en/prog/minerals/mining.html

They may have the data if they are on the Public lands. I am not sure about the private lands for that.