I just wanted to note that I used
cheapvietnamvisa.net. It was $8/person for their standard service, but they actually processed it under 8 hours.
I was completely happy with the service and everything went super smoothly at the border. This is vastly preferable and cheaper than sending it off to an embassy for who knows how long it might take to process.
Oh, and I've never once heard of the limitation on countries where embassies/consulates are ever being enforced.