vtiger, Open Source CRM
With Open Source, you get the product free, the code free & in case of vtiger, you get support free too. That is, till now. A blog post there now asks if the community that is being benefited can give bucks for support. A very valid request, I should say keeping in mind the point that the team that is developing the core project needs motivation & money to keep itself moving.
If you are an Open Source advocate, join the discussion there.