I spend more than $7/month on Highrise (from 37signals) to pretty much do what this does. Highrise doesn't directly support a sales 'pipeline' metaphor so I use tags on customers for each stage ("WarmLead", "ColdLead", "FirstContact"...etc). It's definitely cumbersome to do the pipeline with tags but the contact management and email integration is pretty good.

As a freelancer, I really only use it when seeking out the next contract, which is every few weeks or months. So Highrise is overkill and just slightly too expensive to justify. (But switching to something else never really becomes my top priority.)

One last note: a sales pipeline is useful for many types of relationships... finding customers, hiring employees, getting investors, etc. They all have the same first few steps.