[Genjinaro]

The Twitter App is pretty good, nice work.
Box.net, Shoutcast, Yelp & Orb are my favorites.

If the Facbook app gets a little more functionality (Comments on friends stats & the ability to see all the comments) and the ability to browse the group's pages/fan pages, that'd be awesome.

If anything Windows Mobile lacks, its a decent Facebook experience.

Also Uploading pictures & or videos to Twitter, Youtube, Facebook, Picasa & Box.net would be nice.