By default when you open a new tab in Firefox, it opens with a blank tab. In IE7 the default behaviour is to load the users home page in the newly opened tab. The about:config entry browser.tabs.loadOnNewTab is suppose to allow you to choose to have either the browser startup page, blank page (default), Home Page or Last Visited Page open in the new tab. However, this does not work with Firefox, only SeaMonkey. For more on this see bug 269664 for details.
The extension New Tab Homepage will load your home page (if you have more than one, then just the first page is loaded) in the new tab. That is all this extension does and if you already using other tab extensions such as Tab Mix (Plus), Tabbrowser Preferences or Tabbrowser, then you don’t need this extension as that functionality is already included in these.
New Tab Homepage is about 8 KB.
The Firefox Extension Guru's Blog 
Very simple app. Works perfectly.