To Add Menu Items to SharePoint using Features

Mr Rafelo on his blog has written a very clean step by step approach to add menu items in sharePoint using featurs. In place of his .aspx page you can create your own .aspx page and put it under _layouts folder. And at the last stage, when you are goin to install the feature using command prompt, you may get certain error in that case you need to write -

stsadm -0 -installfeature -filename FolderName\FEATURE.xml

where FolderName is the name of the folder that you have created inside Feature folder.

Rafelo's Blog:
http://blog.rafelo.com/2008/06/how-to-add-menu-items-to-sharepoint.html