Advice on geocoding IP addresses

I have heard about simplegeo api https://simplegeo.com/docs/api-endpoints/simplegeo-context May work for you

IPInfoDB can be used. They don't have a query limit, but they will throttle you to 1 response/sec if you request too frequently.

Alternately, if you feel like writing a little bit more code, you can download their database and run the batch queries yourself. I can't imagine it'd take long to set up, and it will process your 30k IP addresses quite quickly.

google analytics has ip located on a map. I wonder if it could be found in codeplex anywhere?
geocoding-net having the GeoPluginIPGeoCoder();
Also mentioned an issue with the plugin and aquisition of the dat file from... not free geolitecity from Maxmind