Our filtering system (RM SmartCache, but that's largely irrelevant) comes pre-configured with a list of various domains which it doesn't attempt to filter, e.g. windowsupdate.com, anti-virus, etc. I've recently added one more simply because it generates so much traffic that it crashes the SmartCache, accounting for 25% of our week's traffic in 10 minutes! (it is a known and trusted "safe site", so I'm okay with this), but it did get me thinking about whether I should also exclude things like Google Analytics.

What sites do you have set to bypass the filtering?