Warp offers the ability to display a live preview of a space when you move the mouse to the edge of the screen, allowing you to see what you have on another space before actually switching to it. Clicking the preview will then warp you to that space. (Enable this feature by checking the option "Click screen edge to Warp" in Warp's preference pane).
Warp is available free of charge, but donations are appreciated and assist in support and development.
Updated on Mar 08 2011