Batch geocoding using Google or Yahoo.. Free service

http://www.gpsvisualizer.com/geocoder/

This site provides option to give comma / tab separated addresses to do geocode.  It does bulk geocoding of 1000 addresses at a time.

Also, it allows to select the geocode service - Google or Yahoo.

It provides output as longitude, latitude, standardised address, geocode level (street, address, city, zip et.,)

Batch - Network analysis using Arcmap and NA extension

I faced a problem in performing batch process for 50k pairs of addresses (lat.long), to find the driving distance.   I have got a good input for this task,

http://forums.arcgis.com/threads/12128-add-origin-amp-destination-locations-from-the-same-row-to-a-route-analysis-layer?highlight=routename

The above forum link explains how to achieve bulk process in a single click.....

I tried with 50k address sets, ArcMap is able to do process without any issue.