How to quickly lock screen to landscape?
Rotation Locker says that it supports this:


  
  Lock your screen's rotation in Landscape, Portrait or Auto. When you launch the app, you're faced with these three options.
  


For doing this quickly, it does also include a widget to lock whatever your current orientation is:


  
  A widget is provided so you can lock into whatever your current orientation is. (Useful for reverse landscape for example).