I've seen this as an option for a taskbar group but never knew you could select multiple windows. The number of times I've wasted time tiling two non-similar windows (e.g., Notepad and Explorer) when I could have just done this little hack.

CTRL-select multiple windows, right-click and select Cascade, Tile Horizontally or Tile Vertically.

Brilliant!

Courtesy of LifeHacker.