One of the more simple and unused features of google analtyics is the utm_source and utm_medium GET parameters. If you use Google analytics on your site then these are available to you know with NO changes of any code.

Let’s say you send out an email to your friends about your new blog, if you send them to your site with a link that has the above paremeters you can easily look up what effect your email had!

It’s as simple as and then you can see all the traffic you sent under the traffic sources report.

If you are not doing it, then start NOW. Use the Google url builder.