Multi-Meter Dual-Core: Today's Vista Gadget
Multi-Meter Dual-Core has a plethora of different background themes to customize the gadget any way you like. You can blend it with the your Windows Vista background or choose some other shiny motif to suit your whim. It displays real-time info on both your cores, as well as your current memory utilization too. It is fun to watch this gadget go crazy when you load Photoshop or some other CPU intensive app.
The shortcut feature opens the Windows task manager (taskmgr.exe) by default, but can be changed to open whatever shortcut you like when you click it in the admin interface (screenshot below).
There aren't any more options than changing the theme, and changing the path to the app, but simplicity is the cat's meow after all.
The photo is of the regular CPU meter and the Dual-Core multi-meter below it with a sort of green grass theme applied.
Admin interface shot: