Session Save - Saves all the tabs currently open in Chrome and you can launch all the tabs at one click. - https://chrome.google.com/webstore/detail/bbcnbpafconjjigibnhbfmmgdbbkcjfi
Measure it! - Measure anything on webpage. May be a dumb extension for some people very useful for some. - https://chrome.google.com/webstore/detail/aonjhmdcgbgikgjapjckfkefpphjpgma
Offline Gmail - Very useful for people who get frequent mails. https://chrome.google.com/webstore/detail/ejidjjhkpiempkbhmpbfngldlkglhimk
Gmail Checker - This combined with Offline Gmail is a deadly Combo - https://chrome.google.com/webstore/detail/mihcahmgecmbnbcchbopgniflfhgnkff
ESPN Cricinfo - For the cricket fans -https://chrome.google.com/webstore/detail/ijhlikjoigjegofbedmfmlcfkmhabldh
Fb Photo Zoom - Very useful for those who dont want to click on each and every photo on Fb - Actually there are 2 versions i like this one -https://chrome.google.com/webstore/detail/elioihkkcdgakfbahdoddophfngopipi
Google Dictionary - Meanings on the fly -https://chrome.google.com/webstore/detail/mgijmajocgfcbeboacabfgobmjgjcoja
FireBug Lite - YOu know what this does - https://chrome.google.com/webstore/detail/mgijmajocgfcbeboacabfgobmjgjcoja
Tons of Free games to Play.