As mentioned, the easiest method without doing any mods or attachments to your phone would be your wallpaper.
Find an image (via PC) that you would like to use as your wallpaper (or a few), edit them and size them to 480x320 (so they don't get resized on sync later). Then near the bottom add your contact info (like email address or something). Save the image(s). Sync.
Look at your wallpaper before you unlock and how there is a small space below the slide to unlock. This is a prime spot to add some text to your wallpaper. That is all that dumb site everybody keeps linking to does for you but you are stuck with their wallpaper. Might as well do it yourself.
So if found you know somebody will at least try to touch it, turn it on, etc to check it out. And right there on the first thing they will see, is your contact info.