BEWARE of cold-calls soliciting for "charity". A lot, perhaps most of these are outright scams, or done by organizations that donate only a small fraction of what they collect, and pocket the rest.
Google: telephone solicitation police charity scam
or see these articles:
http://abcnews.go.com/Business/beware-charity-phone-calls/story?id=9156841
http://www.michigan.gov/ag/0,4534,7-164-17337_18095-44607--,00.html
http://www.sandiego.gov/police/pdf/crimeprevention/FraudPrevention.pdf
The San Diego Police Dept says: "Scammers often pose as charities and solicit donations for emotional causes such as children with life-threatening disease, wounded veterans, police and firefighters, natural disasters, etc. In many instances they use a name similar to a legitimate charity to mislead donors, e.g., “American Cancer Research Society” instead of the American Cancer Society. They are also more aggressive than legitimate charities, often calling you at home or coming to your door. Keep in mind that legitimate charities, in contrast to scams, will not pressure you to donate on the spot. ..."
The Michigan Attorney General's office says: "The person who telephoned you requesting a contribution was likely not a member of your local police or fire department. Almost all solicitation by telephone is done by for-profit, professional fundraisers, who sometimes keep as much as 90% of your contribution as compensation."