I'm writing a custom add-in to import tasks from our internal support system and was wondering the easiest way to find out:

1. What the current Team Foundation Server and Team Project is?
2. Whether I can add my Import menu item to the Team->Add Work Item menu?

See here http://blogs.msdn.com/hippietim/archive/2006/03/29/563988.aspx for how to get active server & project from your custom add-in.

Add workitem menu is dynamic menu build based on work item types in system and I do not know of a way to add your menu there. You could add a menu under Team or other main menus.