The free WordPress plugin I’ve been using to block comment and contact form spam for over a year is called WordPress Zero Spam:
Zero Spam makes blocking spam comments a cinch. Install, activate and enjoy a spam-free site. Supports Gravity Forms, Ninja Forms, BuddyPress & more…
It only has 20,000 downloads from the WordPress repository which is relatively small compared to other anti-spam plugins. (popular plugins like Akismet has been known to slow down sites and let real comments go to spam).
We did a version of this plugin and offered it as a bonus during a recent launch. We reworked the plugin after the launch was over and we were going to start selling it.
Although I could have made a lot of money, I changed my mind…
Upsell Splash allows you to place “splash” pages that appear before the visitor gets to their content. You can place ANY URL into it and that page will be displayed along with a “no thanks” style link that will close the “splash” page.
We created a sweet little piece of software (or as our friends in the UK say “piece of kit”) that allows you to use Dropbox to deliver streaming video, files downloads, or use Dropbox to host your images all without the visitor having to visit Dropbox.
So for instance, in many of the bonus packages I offer, my mega graphics package is included. These files are really big since they are all graphics modules.