Tim Sneath has posted 30 secrets/tips on his blog. Some of the highlights include the following:

Get Quick Launch toolbar back:
Right-click the taskbar, choose Toolbars / New Toolbar
In the folder selection dialog, enter the following string and hit OK:
%userprofile%\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch
Turn off the "lock the taskbar" setting, and right-click on the divider. Make sure that "Show text" and "Show title" are disabled and the view is set to "small icons".
Use the dividers to rearrange the toolbar ordering to choice, and then lock the taskbar again.

Windows Vista taskbar
Right-click on the taskbar and choose the properties dialog. Select the "small icons" checkbox and under the "taskbar buttons" setting, choose "combine when taskbar is full".

Starting explorer from "My Computer"
To do this, navigate to Windows Explorer in the Start Menu (it's in the Accessories folder). Then edit the properties and change the target to read:
%SystemRoot%\explorer.exe ::{20D04FE0-3AEA-1069-A2D8-08002B30309D}

Old behaviour for Windows Live Messenger
Navigate to C:\Program Files\Windows Live\Messenger\ and set the properties of msnmsgr.exe to Vista compatibility mode. This will place the Messenger icon back in your system tray and remove the 2 annoying tabs on the taskbar.

If you're wondering about the fish in the Windows 7 fish then it's a Betta Fish and also has 7 bubbles to signify Windows 7.

Update: Here's a Windows 7 and Vista (and XP) Simple Multi-Boot Guide.