Is there a key stroke to switch to a fullscreen app in Lion?
You can configure these shortcuts in System Preferences -&gt; Keyboard -&gt; Keyboard Shortcuts -&gt; Mission Control

I think the default is control-option-left/right arrow, at least that's what I have it set to.

In mission control, you can also re-order the position of the desktops/full screen apps by dragging them around. I think by default they're ordered by most-recently used desktop, but you can change that (I can't remember how, that would be a separate question anyway).