If you use Google Chrome and love to fritter away your downtime browsing sites like Flickr and DeviantArt -- or even Google's image search -- Hover Zoom is an extension you simply must install.

It does exactly what you'd guess it would from the name: park your mouse above a thumbnail, and an enlarged version quickly appears. There's nothing to configure -- if you're browsing a supported site (theoretically any site which uses direct links to images), Hover Zoom just works. Hover Zoom's developer has built in a plug-in system, so adding additional sites should be a snap if you're up for a little code hacking.

This is one extension you might also want to enable in Incognito mode -- for those times when you feel like doing some track-free browsing on /b/ or with the safe search filter turned off on Google, for example. Not that you're doing that kind of thing, of course...