Google recently added the ability to add annotations to Analytics. What this means is that you can now correlate trends with campaign implementations in Google Analytics (as opposed to having to cross-reference your trends in Analytics with whatever source you typically use to keep track of these changes). What’s more is you can also share these changes with other users in the account.
In order to add annotations, simply click on a specific date in your trend graph (it doesn’t matter which section you’re in). As you can see below, these annotations can also be shared with users of other accounts.
This makes it easier to correlate historical trends with campaigns and website changes in the past. Sharing this data across teams and departments will also allow more people to correlate data (and hopefully add their own).