A beta distribution of Java and Perl APIs to interact with the NetGeo server is now available: NetGeoClient-1.1.tar.gz

The README.cgi file from the distribution provides some rough documentation. You may also find looking at example scripts useful.

If you simply want to find the lat/long of a large number of ASes, it will be faster to download and parse the automatically generated file at http://netgeo.caida.org/aslatlong.txt. This is generated every Saturday at 10:30pm, Pacific Standard/Daylight Time, and contains a mapping from AS numbers to AS name, country, and lat/long.