http://ppcgeeks.com/ring-toggle-hard...tan-t8079.html
This links to a ring-vibrate toggle Cab that was posted on another HTC forum at XDA. The file takes up little to no space and doesn't require the loading of a visible interface and as such is rapid on and rapid off. I use the Comm Manager button as my Virbrate/Ring toggle now. Works great. To get to the Comm Manager, either waste a slot on a Today screen launcher or just click the connection icon in the top toolbar and select Comm Manager from the pop-up.