Welcome to the board Chris,
I assume that you are looking at getting a Tourist Visa to China so that is what I will go over. As KFC has already pointed out, visa applications can not be mailed directly to the Chinese Embassy or one of the Consulates for processing, someone actually has to physically submit it to them. However, you can mail your passport and visa application to a visa service who will then submit it to be processed on your behalf - this is what most people do (including myself). Unless you live near the Chinese Embassy or one of the consulates (DC, New York, Houston, Chicago, LA or SF) then this is the best way to go. Using a visa service is very easy to do - I just submitted my 4th visa application last week and am expecting my passport back with new visa in the mail today. I also used a visa service to obtain my son his first Chinese visa several months ago without any problems. I always use China Visa Service Center (
www.mychinesevisa.com) and each time have been more than satisfied with their good service.
Your best bet is to request a multiple-entry visa. The multiple-entry visas are valid for 12 months and usually have a maximum stay period of either 30, 60 or 90 days (depending on which consulate your application is submitted to and how you ask for it) with 60 days being the most common. Multiple-entry visas valid for 24 months and extended stay periods are only available to those who have Chinese national family members - this is the visa that I get. All visas cost $140, so always go with the multiple-entry visa - this will allow you to make multiple trips in one year and also allow you to reenter China from Hong Kong if that is in you itinerary (I always seem to make at least 1 trip to Hong Kong while I am in China). If you use a visa service you will need to add $40-$45 to the price of the visa. You can pay either by check or credit card when using a visa service.