I doubt something like this exists, but I thought I might as well ask.
I'd like a way to hide certain icons in the dock that I don't really need up. For example, I control iTunes through my logitech keyboard (usually just pause/play, skip, or prev in party shuffle). I don't really need iTunes down there. Now, I've heard you can edit a plist on a per-app basis and get an app to not show up, but what do I do on those occasions when I would like to switch to iTunes to find a specific song, for example?
I really like the dock, so I don't want to get rid of it, and I'm not a big fan of hiding it (I don't like moving targets, and I like seeing stuff with badges all the time). However, between Safari, NetNewsWire, Adium, Finder, iTunes, Mail, and the Trash (I prefer it in the dock) all there, I've pretty much always got 7 icons down there.
As Growl matures, a lot of these things I don't feel I'll need down there all the time. I won't need a Mail icon, as notification can be moved out of the dock and through Growl (I'm making this example up, so don't worry if Mail and Growl aren't friends yet)... but when Growl shows up with a notification saying I have new mail, I'd like to be able to say hit a hotkey and have icons I hid all show up so I can check Mail... same would go for NetNewsWire, I could just check when Growl tells me to.
So... is there anything out there that does this? Perhaps one of the many variations of the multiple docks idea will allow me to hide a bunch of apps in a certain dock and not have them show up in other docks while running? Any other ideas? Thanks!