Add-ons that start with the letter K, are Free and are sorted by Most Recently Reviewed.
KeyAds allows you to display content to your visitors—like an ad or block of HTML code—based on keywords they enter in a search engine, or based on the referring domain.
Just another graphic captcha (based on kCaptcha).
Keywordz will take an input string and outputs a comma-delimited (meta) keyword string. Common and duplicate words will be removed from the output string.