I registered as a developer with the Android Market today. I wrote a simple utility app a few months ago. It displays the IP addresses assigned to each network interface on the phone.
I whipped up a logo and uploaded the app to the store with the name of "WhatIsMyIp?".
Update: the app has been on the market for almost 48 hours. After the first 16 hours, there were 160 installs. after 24 hours, there were 241 installs. As of 8am this morning or 36 hours after publishing, there are 546 installs with 443 "active". I assume active means still installed (80%) and the rest uninstalled the app after trying it.