My old Samsung has a widget based home screen which allows free placement of icons and widgets. You can even overlap them, which is great.
I imagine if it was possible under android Samsung would have done it already with their touch wiz UI (which my old samsung used a version of) so it may not be possible with current versions of android.
But if someone managed to do that, they'd be on to a winner!
I've just given Zeam a try after a few reccomendations. It's not bad actually. Simple and basic, but not without it's charms.
For people using ADW, or Zeam, who want Launcher pro style widgets, the best I have found so far is 'Colorize Widget', free from the market. It comes with matching Facebook, twitter, messages, bookmarks, contacts, agenda widgets... only thing really missing is an email widget and a grid calendar... but even launcher pro doesn't have an email widget for some reason.