My iPhone is running 4.0, so it uses a background image — I’m currently using this excellent one from Marcelo Marfil. It’s important to find something dark and low contrast for this. With the apps, there’s something I like about keeping the home screen pretty default. That said, you’ve obviously got to break out here and there:
Facebook — I tried taking this off my homescreen, but Facebook wouldn’t let me.
Tweetie — Swoon. Everyone knows this rocks.
Now Twitter.
Things — The best to do app I’ve used to date, my only complaint being its dire, dire need for a cloud-based syncing method (I also use on my laptop and iPad).
Tumblr — I run quite a few blogs on Tumblr, the biggest being 9-bits, WebKitBits, and Ext, so it’s nice to be able to check in on notes and comments pretty easily.
In regard to the organization of apps: The first row is mostly communication, with the exception of Things — I explicitly set Tweetie and Things to be top-right as their my most active apps hitting and I find top right easiest to hit with my thumb when holding the phone (a bit anal, I know). The second row is Date/time and Photos. Third row is writing and live info, last row are the two stores. The dock is totally default.
I’d feel remiss if I didn’t also mention just a few of my favorites past this screen as well, like Gowalla, Ego, Boxcar, and iTeleport.