Google Analytics supports an interesting feature called campaign tagging, where you append variables to a URL so you can track a “campaign.” You could, for instance, add them to the URL of a post of yours that you will be sharing on Twitter. Then you wait for it to propogate and go viral. You can then track, in Google Analytics, how much traffic is coming from Twitter. Usually, Analytics won’t be able to give you an accurate picture of how many hits are coming from Twitter, as it only sees visits from Twitter.com. Traffic from desktop clients like Twhirl and TweetDeck appear as direct visits. Campaign tagging fixes that.
Jack McIntyre recently cooked up an interesting plugin for WordPress, one that I’m surprised hadn’t already existed. It’s called Tracked RSS. It adds campaign tags to your RSS feeds, so you can tell when someone clicks through from their feed reader to your site. This is something I’ve long wanted to do. There’s also a sister plugin, Tracked Tweets, which tweets your posts and includes campaign tags in the shortened link.