Oh, lets see.
Zenbe lists - freaking useful for shopping, to do's and tasks, etc.
1Password - handy if you use the desktop client
Bookmarks - delicious bookmarks, couldn't live without it
Twitterrific - fav Twitter client
Evernote - note syncing is a must
Remote - for obvious reasons
Stanza - e-book reader
Wordpress and Tumble - for blogging
Flickup - uploading photos to Flickr
Wikipanion - Wikipedia viewer
Shazam - great for finding that song that you don't know the name of
Topple - my latest iPhone game addiction
LineRider - great time waster
Yes, there's more, but that'll do