gofish reverses points to countries. It supports single point reversal via a web api or batch reversal given a file of points.
Make sure you have the Two Fishes server running.
Start the gofish server:
$ go build
$ ./gofish -a :9090
2013/09/23 11:12:08 server listening on :9090..Point your browser to http://localhost:9090/reverse?ll=59.329,18.068
Create a file of points called points.txt, one point per row ([lat]\t[lng]\n):
59.3137 18.0669
52.5206 13.4026
59.3277 18.0087
47.625 -122.515
Batch reverse the points, group results by country:
$ ./gofish -batch.points points.txt
2 Sweden
1 United States
1 Germany
Reverse without grouping:
$ ./gofish -batch.points points.txt -batch.group=false
59.3137 18.0669 Sweden
59.3277 18.0087 Sweden
52.5206 13.4026 Germany
47.625 -122.515 United States
As advertised at http://twofishes.net the performance is at least 1000 reversals/s. I've even seen it come close to 2000 reversals/s.
gofish uses country data from http://geonames.org to convert country codes to country names.