Bookmarklets are, IMHO, being used for more and more funky functions.
I really like the Facebook and Tumblr bookmarklets that scoop out information about the type of content you want to post and then sends them off to the respective sites.
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So prompted by this opinion, I've compiled a list of tips I've learnt from writing various bookmarklets, from simple jQuery injection to the Speech Bubble app.
Please have a read if you're interested in Bookmarklet Coding.