Browsing? That’s so 90s. With the myriad of available Firefox plugins,
you can do pretty much anything with your favorite browser, and many of
these don’t have anything to do with browsing the web.

From managing
your groceries with Firefox to playing classic arcade games offline, we
present 19 browser extensions that have nothing to do with, well,
browsing.
Time Killers
Cards -A collection of solitaire card games including such games as Aces Up, Double Klondike, Double Solitaire, and many more.
Clines - An addictive game in which you must build colored lines to win.
Froggr - Relive the classic arcade game, Frogger, from the comfort of your favorite browser.
Mines - Another classic game - Minesweeper - in your browser window.
Mozteroids - A variant of the classic arcade game Asteroids you can play in your browser.
Pag-Man - A Pac-Man clone with a two-player mode.
PingPong - For those people who find playing Pong against other people too difficult, you can just play against the computer.
PONG! Multiplayer - Play a game of the classic game Pong while chatting with people online.
Snake - A clone of the popular game Snake and Worm.Read more..