Hi readlady. Although the people are trying to make you feel guilty, only you can make yourself feel guilty. Don't make them make you feel guilty. I know this is hard to do but do it!
In your place, I would kindly tell them "I am not available to donate at this moment". If they would ask me why, I would tell them "There are personal reasons which I wish not to discuss right now". This has a powerful effect.
You didn't specificy whether you are doing it by phone or by person, but the concept is the same.
redlady said:
What do you do when someone collecting for charity gets a hold of you and not only gives you a good spiel about the charity but a nice big serving of guilt to go with it ? If you had anything you would right, despite telling them this they just wont give up the gulit trip - so what would you do to get out of it ?