[TriLUG] Open Source alternative to ACT! on Windows?

[bp]

My father is in the process of taking bids from Dell for a server 
running ACT! on Windows Server.  I haven't seen the bid yet but I'm sure 
it's a fair bit of change for a 5-10 user license of ACT! and Windows.

Are there any Linux/Open Source CRM project out there that I might pitch 
over the MS/ACT! duo?

Perhaps browser based clients?

Thanks,
bp