Ken, Gravity Forms has a "spam honey pot" that you can turn on, which helps a great deal. It is kind of the opposite of GASP, as it is a hidden field that only the robots will fill in.
The other option I've used with great success is an "are you human" question. Questions you could ask include: "are you human? answer 'yes' or 'no'" or "is fire hot or cold?" or "what is the sum of 1 + 2? (hint: enter '3')". See http://www.brego.net/about/contact.php for an example.
The trick there is that you need to have your code check to make sure that the question was properly answered. You may also want to handle the "oops" factor by giving visitors another chance if they didn't fill it in properly at first.