This currently seems limited to sending forms via e-mail or providing a link to a form at Google. It's quite easy to embed a Wufoo form in any webpage.

Also, I just tested the system. After submitting an e-mail form, I got this nice error message on a pop-up web page:

"Something bad happened. Don't worry, though. The Spreadsheets Team has been notified and we'll get right on it. Sorry about that."