I agree with Loren that the default arrangement (prior to 3.0) is the best aesthetically, but lately I find myself using the default apps — such as YouTube, Stocks, Weather, etc. — less and less.

After performing an ‘audition’—where in I leave the home screen blank until I need an app, then move it to the screen—this is the arrangement I currently have:

On the Dock: Messages is the most used app on the phone, Mail is great but I’d love a unified inbox, Tweetie is my favorite app (for any platform), and Camera so I never miss a shot.

Phone — I rarely use the Phone app, so it has traded places with the Messages app. Since it’s still a ‘mission critical’ app, I keep it in the top left corner, easily accessible.

Calendar — I sync with both MobileMe and my work Exchange Server, and mostly use the Month view.

Photos — default location, easy to find.

iPod — opposite corner of Phone, also critical-but-not-Dock-worthy.

Things — to keep me on task, syncs with the Mac version.

Notes — the perfect notepad for quick thoughts, meeting notes, etc.

Bible — The best Bible app for the iPhone, though I wish it were more fully-featured.

Clock — my alarm clock.

Deep Green — the best chess game for iPhone. Beautifully designed, terribly difficult to beat.

Words with Friends — Scrabble with friends (and strangers) at my leisure.

ScoreCenter — before ESPN released this app, the iPhone was incomplete. (I still wish there was a Weather-like scores app.)

Facebook — obligatory placement to remind me to actually try and care about Facebook.

CNN — great interface with nice local news features and live video.

Safari — best app on the iPhone.

TweetDeck — to keep pulse on trends, searches, and mentions (for @thecitychurch).

Settings — needs no explanation.