The U.S. Department of State provides an online tool that you can use to estimate how long you will have to wait to get an interview appointment to apply for a visa.
In addition to interview wait times, this online tool will also tell you how long it will take for your nonimmigrant visa to be processed at the Consular Section, after a decision is made by a Consular Officer to issue the visa and the visa is available for pick-up by you or the courier at the embassy. Please note that this processing time does not include any time required for administrative processing.
You will not find information about K or V visas using this tool, since these visas are processed similar to immigrant visas. A and G visas are also excluded.
Source: Department of State