Chrome: I love a good GIF party as much as anyone, but if I'm on a page with a constantly looping animation, it gets on my nerves pretty quickly. Google just released a Chrome extension that allows you to block animations entirely, or set them to play only once.
The extension is incredibly simple: install it, click the button in your toolbar, and decide whether you want animations to play forever, stop after one playthrough or never animate. Simple, huh?
We wish it would give you per-site settings, or maybe allow them to play twice through (I sometimes miss them the first time), but overall it's a useful tweak if you spend a lot of time around GIFs. Alternatively, you can try GIF Blocker, which won't play GIFs until you click on them.