Chrome extensions I find useful:
Google Mail Checker This extension automatically checks your google mail so you don't have to keep manually checking.
Urban Dictionary Search This extension enables you to quickly search for a meaning of an urban word you do not know the meaning of.
AdBlock One of the best extensions for Google Chrome to date. This blocks basically ALL advertisements over the net. Including youtube videos!
View Thru This is a pretty nifty tool for fishy short url'd links, you hover over the link and it displays the whole link.
Facebook Photo Zoom This is also a great time saving extension for Facebook users, simply just hover over an image thumbnail and it shows the full image. No more clicking next non-stop.