I've been using Drupal for 2 years now and have been itching to contribute back to the community that has given me so much. The module, Spamicide, is designed to be another tool in preventing comment spam, bogus users, etc, and it doesn't require user interaction at all, which I think is better for the Drupal community as an enhancement to usability.

Spamicide adds an input field to each form then hides it with css, when spam bots fill in the field the form is discarded. The field, and matching .css file, are named in such a way as to not let on that it is a spam defeating device, and can be set by admins to almost anything they like(machine readable please). If logging is set, the log will show if and when a particular form has been compromised, and the admin can change the form's field name (and corresponding .css file) to something else.
The install routine sets some default forms as a minimum defense, and admins can turn it off for these, but it's not suggested, it's really the reason it was installed.

It should play nicely with the CAPTCHA module. Not sure about the Mollum module. You may very well decide that this does the job all by itself.

Wish list: I'd like to add localization, however I would need help to add translations to it.
The version for 5 is feature complete.
The version for 6 has the same feature set.
I truly believe that the functionality and usability may prove so useful that (dare I hope) this idea may become part of core for 7.