For all US citizens, the Indian government uses a visa service company called Travisa to process visa applications. Travisa can usually have a visa issued and retuned to US citizens in about 2 weeks. The cost of this service is $70.00 for a 6 month visa.
Travisa does offer an expedited service, but it's always best to submit your applications 6-8 weeks prior to your travel date just in case the Indian government needs more information on your application.
The cost to expedite your visa is $99.00.
You MUST purchase your airline ticket prior to applying for your visa. This is a requirement of the Indian government in the application process.
If you are a foreign National, legally residing in the United States, you must have a valid Resident Alien card or visa issued from the US government, which allows you to travel outside of the country for up to 30 days.
The visa processing fee for foreign nationals legally residing in the US is slightly more expensive, and ranges from country to country.
Please check Travisa's website for an exact cost.
Travisa has offices in the United States, Canada and London. For all other countries, please consult your local tourist resources.