Just downloaded and set this one up last week. It is free and server based if that matters to you. I was using one of microsofts overpriced and bulky business softwares, but it does more than I could ever need so I am in the process of looking for something else too, either p.c. or server based.
http://www.sugarcrm.com/
Searching over the last week I have come to the belief that people are really proud of their software whether it is worth it or not.