Obvious choices for XBL games for me are:
Chest Games (both)
As far as apps are concerned:
BBC News Mobile
My Football (brilliant but needs one or two more updates to be perfect)
Weave (RSS Reader, ditched it for Wonder Reader)
Lazyworm Youtube can help you hold until Microsoft release a real Youtube app but it's not brilliant.
Ustream Viewer is shit but at least it's there so we can hope for updates.
Edit: Update released, seems fine now.
Engadget app is on the way according to their podcast.
A few reviews are available on wpcentral.
Anything guys can't live without or would definitely recommend?