Happy, tiny Gmail tip
Click a message checkbox, then, holding shift, click another one a couple of messages apart — all intermediate checkboxes are automatically checked.
One of the most universal uses of the Shift WP key is to aid in selecting ranges (think how you use it to select text or several files) and yet it was only today that it occurred to me that it just might work for checkboxes. I blame years of crappy webmail for that. I checked Hotmail, Yahoo! Mail (the “standard version”, the cool beta version does implement something along these lines), and my university mail and it won’t work there — which is bollocks: it’s a tremendously useful feature that costs near nothing to implement.