Drupal has several modules that provide support for the "email this page" type of feature. For example, you can use the one of the modules that allows you to share a page to various Web 2.0 social networking sites.

One module to consider is Sharethis (http://drupal.org/project/sharethis). It combines the ability to share the page to sites such as Diggit and Facebook and includes the option to email the page to an address you provide.