It is not immediately obvious how to use ibrowse to send an HTTP POST request with form data (perhaps to simulate a web form post). Turns out its pretty simple:

ibrowse:send_req(URI, [{"Content-Type", "application/x-www-form-urlencoded"}], post, FormData)

Where URI is where you want to send the request ("http://some.server.com/path/to/somewhere.php") and FormData is an iolist() of URL-encoded values ("foo=bar&fizz=buzz"). There's obviously a lot more that can be done, but for a quick snippet, this is pretty sweet.