Is there a way to set cookies

Is there a way to set cookies and capture the traffic source when a visitor becomes a member?

Here is what I am trying to do. I have a bitly link which is different for each traffic source (I have a few hundred different sources). The links go to specific landing page, this allows me to track which source the visitor comes from.

On the landing page there is a ‘become a member’ link, which the visitor clicks to register. However, when they go to register, I now don’t know which sources, they came from. What I would like to do is be able to capture that information when they register and hold that information in the user database (along with name, password, etc). Is there a way to do this?

There is one more issue, the visitor may come to a landing page, click on a different page, before becoming a member (so its not always direct from landing page to registration). I would still like to capture the information.

Thanks,

Ray