Not much around Nashua. Right downtown is Millyard Brewery and Martha's Excahnge and in Merrimack is Able Ebenezer's. I haven't been to Millyard yet, Martha's is more of a restaurant and I wasn't overly impressed with Able.
If they doesn't mind driving 20 minutes east to my area, there are several breweries in a fairly small area.
From the Barrel
Moonlight Meadery and Hidden Moon Brewery
Great North Brewery
Pipe Dream Brewery
The Derry and Londonderry locations are all within a couple miles of each other. The Manchester ones are just a few miles away. Check their pages for hours since some don't open during the week until Thursday.
If they are in the area for a few days and want to take a little drive, there are tons of great places out in the Portsmouth area (about an hour and ten minutes away from Nashua). Stoneface, Earth Eagle, Throwback, Smuttynose, Great Rhythm, Tributary (just over the bridge in Kittery - Tod Mott's brewery. Tod was one of the brewers than developed the Harpoon IPA recipe).