Kodak were running demonstrations of Prinergy at IPEX last year and they simulated different users by switching desktops using
VirtueDesktops. I think the guy was a bit ticked off that my one question after the presentation was about the virtual desktop software. Turns out VirtueDesktops is the continuation of the Desktop Manager project which was discontinued some time ago, apparently. VirtueDesktops certainly has more features, and is available as a universal binary.
I also use
Mail Unread Menu because it's nice and unobtrusive; I have my dock on auto-hide so I don't always see the notifications. Plus, my Mail sits in a different desktop
Whilst on the subject of Mail, there's a nice plugin called
Letterbox, which switches Mail.app to widescreen mode. As a former user of Outlook, I'm more used to this orientation and it makes better use of my widescreen display too.
Finally, I know VersionTracker already covers this and more besides, but I like it at
iusethis where you can tick off which apps you use, then see
what others are using.
For the record, I'm not afiliated with any of the above, although on re-read I sound like a fanboy

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