[CentOS] Centos 5.1 + Open source CRM

I hope someone has implemented Centos plus some open source crm, what do you
recommend ? I already googled a lot, find a lot of open source related
things but I need to hear from someone who uses it or implemented in the
past to try something like that, I don't have to much experience in nix
world but I can try it.

Thanks in advance for all who want to contribute in this matter.

Cheers 

Jorge from Uruguay