I've developed a plugin, using the Akismet API to filter out all spam, for the Contact Form, Product Reviews, Blog / News Comments, and of course, the forum sections.
I'm looking for a couple of people (hopefully have an issue with spam, although most of us do), that are willing to test it for me. You'll need to be using nop 4.40.x, and the test version will only work on the contact us form.
You can create a free account with Akismet, as well as paid accounts, or get a developer key.
The full version will be licenced and will work on all forms where spam could be sent.