There is product called Optin Professional Toolbar for Joomla, it provides a popup at the bottom of the users browser. http://www.pluginvalley.com/demos/optin-professional-toolbar-demo.html
Is there a feature within CMC - MailChimp for Joomla! that would enable me to do the some thing like this. Instead of a signup form within a module position I would like it the be on a tab that either sits at the bottom or on the side of the users browser.