The Browser Window Resizer, a Firefox extension, is useful for testing different screen sizes. It accurately resizes your browser so you can test to see what a web page looks like in all of the standard resolution sizes.
Supports the 640x480, 800x600, 1024x768, 1280x1024, 1600x1200 resolutions.
Resize the current page via the Context menu, Tool menu or Toolbar button.

Turn Watcher is an Initiative Tracker for RPG Game Masters! Use it to: Track PCs and monsters easily during combat; Handle delays and readied actions; Secret Spot & Listen checks and Will saves without your players being the wiser; Manages hit points of PCs and monsters; Import monsters into new encounters quickly and easily; Add that edge to your encounters by automatically rolling initiative every round without picking up a single die!