VisaMapper – This site maps the visa requirements for every country in the world.
ProjectVisa.com – Visa and embassy information for all countries.
VisaHQ – Travel visa requirements by citizenship for every country in the world.
VisaForU.com – Visa knowledge base covering topics related to visa and travel requirements for all countries.
Visa Processors – UK
MyVisaAdviser – Apply for visas in London.
Visa Processors – USA
VisaCentral – Visa application concierge service.