[rwhitman]

Salesforce does have a non-profit tier that's heavily discounted. May be overkill for your case but it's an option

[syntern]

Is this for official US non-profit status organizations, or for ad-hoc and non-US communities too?

[jamram82]

Check out http://www.salesforcefoundation.org for more details.

[rwhitman]

They have account reps you can talk to and make your case. Worth a shot