Simple web service using Amazon SES

Question

I would like to use AWS and especially Amazon Simple Email Service (SES) in order to setup a webservice allowing to send emails.

Emails would be triggered by some kind of POST request to the webservice with some authentication, and the webservice would then just send the email on behalf of the web service user.

Where should I start? The webservice part looks dead simple but I'm not familiar at all with web services. I still need to run some kind of multithreaded webserver since there could be a bunch of concurrent requests.

Is there a way for me to write a very simple web server in Ruby or Java to do that? Any pointer appreciated.