Google has a very extensive list of alternatives, both free and fee for service:
https://code.google.com/p/gmaps-api-issues/wiki/NonGoogleGeocoders
(accessible as of 8/2015)
Texas A&M also has a list: https://geoservices.tamu.edu/Services/Geocode/OtherGeocoders/
(also accessible as of 8/2015).
I provided links rather than cut and pasted the contents because the pages are more likely to be up to date.
