How to track the traffic sources (like affiliate, email etc...)

I wan to track the traffic source from where the visitors are coming to my sales page.

What is the best way to track that and which service/script should I use?

I want the report something like:
========================================================
Date Traffic Source Unique Visitors Sales
=========================================================
10/11/2010 email 2569 3
10/11/2010 affiliate 9258 7
10/11/2010 search engine 6258 2
10/11/2010 forum 200 0
10/11/2010 others 4568 1

 

Thanks, Shawn for the suggestion.

How can I tell google analytics about from where my traffic is coming from?

 

well they can't track the email source in google analytics as it would show as "direct/no referrer" just put ?campaign=email2 or ?campaign=digitalpoint at the end of your email/forum/whatever urls