I have the captcha image module and an email address keeps spamming me in a website feedback contact form. I do not know how to get their IP address and I do not want to take down the form for the public. Any suggestions?
That is why Mollom exists: http://drupal.org/project/mollom
Mollom may block a post outright if it is from a known spammer. If Mollom is unsure how to classify a post, it may require the completion of a CAPTCHA to accept the post. Posts that do not match a "spammy" text pattern and do not originate from known spammers are accepted without the need to complete a CAPTCHA.
A stand-alone CAPTCHA solution, which neither considers user behavior nor point of origin, can never achieve this level of informed protection, and generally requires users to solve a CAPTCHA on every post. Using Mollom's text analysis, users must only solve CAPTCHAs when Mollom is unsure about a post.
Try the reCAPTCHA module. It's worked brilliantly for me.
You can try out the Honeypot module. It basically adds a hidden field to your forms, and then makes sure it is empty upon submission.