In OS X Lion there is the possibility of screen sharing. I wonder how to access my Mac from my iPad without installing anything on the Mac
You can try enabling Screen Sharing (in the "Sharing" preference pane of the System Preferences app) on your Mac. This will start a VNC server on your local machine. You could then install a VNC Client on your iPad (Mocha Lite is a free one) and view/interact with your applications.