I'm looking for software that a brand-new, very small nonprofit could use to keep track of donors (and potentially other kinds of supporters, like event attendees and email-list subscribers).
We have literally no money right now, so I'm looking for something open-source (or at least free-as-in-beer). We also don't need or want anything very complex; we're at the stage of asking friends and family right now, so our needs are really basic, but I'd like the organization to start following best practices from the beginning.
None of us are primarily development professionals (development in the sense of fundraising), so the ideal program would be useful, and potentially scalable, but should not have an especially steep learning curve. We want the program to make us work smarter, not to be a net drain on our time.
Miscellaneous needs: Everyone at the organization has Macs, so native OS X support would be ideal. Linux-only solutions would also be ok, but Linux support is not necessary. A Windows-only program would be considered only if it was so good as to be worth setting up a virtual machine or dual-booting. If it is possible to work with the same list across multiple computers/users it would be a plus, but it is definitely not a requirement: only one user needs to work with the program regularly.