My home screen is incredibly boring. Because I have a few devices, and I do a lot of testing with them, I also have to restore them fairly often and it's gotten to the point where I just leave everything in its default location because it's a) easier than rearranging and b) I don't have to hunt for stuff I haven't rearranged.
So, my second screen has become where I move my non-default, but still more often used apps. Typically the exact order will vary due to the reasons above, but the apps are fairly consistent.
I'll list out what I use after the break, but we're really more interested in what's on YOUR iPhone home screen and why. If you're willing to share a screenshot, jump on over to our TiPb iPhone Forums, attach it, and share the details!
My screen: Top row is secondary Apple apps, which I use once-and-a-while but like to refer back to.
Next is UDID so I can quickly get an Ad Hoc distro set up if I need to test something. 1Password is typically the first thing that goes onto my Macs and iPhones. Life. Saver. BeeJiveIM is for those rare occasions I keep IM on, on the go. Qik is the Ad Hoc version that actually does stream live (Apple/AT&T need to approve that version now).
TWiT.am is for when I want to listen to streaming Leo Laporte. Wikipanion gets hit often for pop culture reference. Jaadu hasn't been set up in a while, but I dream of it working for remote desktop one day. Skype just came to Canada, but only works on full bar WiFi right now.
TwitBit 2.0 is what I'm testing for Twitter right now. Tweetie is just so Apple-like I often default back to it for power posting. Shazam is Shazam. It might get banished to a lower screen soon. Navigon keeps me from getting lost, which I am wont to do.