Here's a small AutoHotKey script that: Note: the compiled executable must be run from Program Files on Windows Vista and newer versions of Windows, otherwise it won't work properly.

WheelAltTab32.exe - 32-bit version
WheelAltTab64.exe - 64-bit version
WheelAltTab.ahk - source code

Update 2015-07-31:

Since Windows 10 includes the ability to scroll under mouse pointer, here's a version of the script that just implements Alt+Tab and doubleclick.

Update 2015-08-07:

Now also sends Win+Tab when Back+Forward buttons are clicked.

WheelAltTabNoScroll32v2.exe - 32-bit version
WheelAltTabNoScroll64v2.exe - 64-bit version
WheelAltTabNoScrollv2.ahk - source code

And by request, version that only scrolls the window under mouse pointer.

ScrollOnly32.exe - 32-bit version
ScrollOnly64.exe - 64-bit version
ScrollOnly.ahk - source code

Update 2016-06-09:

All files now also include a SHA-256 signature.