I want to teach English as a Second Language here in the U.S. Where can I get certified to get started?

When I was younger I considered being an ESL instructor and traveling abroad. I'm older now and the traveling overseas aspect of it is completely unappealing. However, I still want to be an ESL instructor. I have a Bachelors Degree in Liberal Arts, and lots of professional (though non-teaching) experience. My initial research indicates I'll need an ESL-teaching certificate to start. And that's fine. But from which institution? There are many choices, and I want a quality certificate that I can use to "trade-up" to a bona fide Masters Degree.