OnTopReplica!

Like the "Always on Top" feature that some programs have? TurboTop lets you set any window to be "Always on Top!"

Duplicate Windows visually copies any window in Mac OS X live and on-the-fly. It’s like display mirroring for individual windows! I created the tool to display windows across multiple monitors in extended desktop mode during presentations. It’s proven useful to watch web videos over other windows as demonstrated below, or to keep an eye on windows I’m not actively using. I’m certain that there are yet undiscovered uses for such Duplicate Windows.

Keep windows afloat (heh) on top of all others.Pin windows to the desktop.Move windows from anywhere, not just the title bar.Turn a window into an "overlay" on your screen that doesn't hinder your work.Show a window's file in the Finder with nothing more than your keyboard.Resize windows from anywhere, not just the edges, and more.

Sticky Previews is a lightweight productivity tool that lets you create live previews of any window or a screen region of your choice. It keeps previews above all other applications like a sticky-note thus allowing you to monitor any background window in real time no matter which application you’re working with at the moment.

WindowWatcher is a free hybrid window magnifier and remote control spy. It gives Windows the ability to have proper and resizable picture-in-picture support above and beyond Aero Snap. It's great for watching stuff like online TV, streams or Youtube playlists in a small corner of your workspace while working in the rest of it. It's also a fantastic help for tasks that would otherwise require flicking back and forth between windows, or to provide a simple pop-out viewer for websites and apps that don't have their own. »