Well, define "at once." I'm assuming you mean within the same nano-second, which, for the most part, would be the exact same time. If this is what you mean, no.
You could submit one, then submit the other, however, but that would be much slower. You'd have to use JavaScript, and probably an iframe or a frameset so you don't lose data from the other form.
Why would you want to submit two forms, anyway?
