I posted this in the promotions category but no feedback as of yet. I need to move a little quicker and thought you all might have some thoughts.

Can anyone offer any advice on creating a way to track sales from leads, much like how it is handled by google adwords?

I use Adwords, but also have other links I would like to track from some banner ads, email newsletters, and general directory listings.
I also have some offline stuff that I could use a special url for if I had a way to track from entry point to sale.

Any thoughts? I have no experience with cookie creation but I thought that would be one way to go, or perhaps use an online service, if there is such a place that can provide this service.

I currently use Hitbox to monitor the site, but it is not a tool to really track conversion / sales from multiple sources, especially when the sales cycle is a few days to a few months.

thanks for any thoughts or suggestions.