Gnome extensions site

Gnome how have a web site where users can install shell extensions, just like Firefox users can install add-ons at the Mozilla site. What I really want to see there is an extension that will allow me to get the functionality of Alt Tab with a mouse click on the panel, maybe next to Activities.

Gnome 3 mockups

[Update, June 2011: for some reason this page has been getting a lot of hits recently. Gnome 3 has been released, people. If you want screenshots, visit the Gnome 3 site for screenshots of the finished product.]
I found some screenshots of the new Gnome 3 mockup on the Debian forum. (The Gnome 3 release has apparently been delayed to accommodate the changes.)
I'm looking forward to using Gnome 3. The present desktop model in Gnome dates back to 1995. Time for a change. I've used the Gnome 3 shell in Ubuntu and (briefly) in Fedora and liked it. In both distros it caused computer lock-ups, but I'm pretty sure these were due to using it with Compiz running at the same time. Now I'm running Debian Stable, where the Gnome shell is not available. If Gnome 3 comes out in March, I guess it will miss the next release of Debian Stable too (due around the end of the year). Sigh.

Destop design (1995-2010)

I've mentioned recently how I like to minimise applications like music players to the notification area, and talked about alternative method of minimising to an icon- using a dock.
Now I learn that Ubuntu is set to kill its notification area.
I quite like the old system of minimising documents to the taskbar and putting running applications in the "notification area"- system which apparently originated with Windows 95 (although the "abuse" of the notification area to hold any old application came from third-parties, not MS).
How to avoid running applications in the notification area? I learnt recently that a lot of Ubuntu users have applications like music players running full screen on a different desktop and simply switch desktops. Seems like a good solution, but I've never really got into using more than one desktop.
I recently came across a way to see what's running on different desktops and switch between them, using Compiz and the "Windows" key. The keyboard short-cuts Super (aka the Windows key) + W brings up all desktops and shows what's running. It seems there are a lot of useful Compiz keyboard short-cuts I never knew about.
The way the short-cut worked reminded me of the Gnome 3 shell, which I've been trying out recently- clicking on Activities in the shell opens a window with the desktop or desktops, plus a panel menu.
As a way of organising open applications, I'm going to try having four desktops, and running one application full screen on each desktop. For somebody who has been using the taskbar and notification area for so long, it'll be a case of teaching an old dog new tricks, but with any luck the dog is not yet too old to learn.
The Gnome 3 shell is due for release in September 2010.