This tell-a-friend script can be used for any email function.
Developer: Lyle Hopkins Platform: linux, windows, freebsd, osx, sun Date upd:2005-06-17 Hits1220 [Download] [Visit]

What this does is simple. It allows visitors who visit your website to refer friends to your site easily. The script provides a thanks page and a button that will return them to the exact page they refered their friend from automatically.
Developer: Perlcoders Platform: linux Date upd:2006-02-19 Hits534 [Visit]

Site Referral Pro is an advanced site referral program. Main features include: a hit counter, online html form generation, online email generation and more. A ClickBank version is also available!
Developer: sitereferralpro.com Platform: Linux, Unix Date upd:2001-10-08 Hits724 [Visit]

eRS (eRecommend Site) allow visitors to send (Recommend) an e-mail message about your site to friends simply by entering the email address (and name optional). It's ensure that two good email addresses are entered to avoid anonymous spamming. The message and result look page
Developer: ftls.org Platform: Unix, Win NT Date upd:2000-08-13 Hits3356 [Download] [Visit]

Give your visitors the opportunity to mail the contents of your web page to their friends or themselves. Master Webpage Mailer allows you to determine which parts of your web page get mailed. You determine the text formatting of the resulting email. Master Webpage
Developer: willmaster.com Platform: Unix Date upd:1999-12-17 Hits1809 [Download] [Visit]