Simply replace the unfilled areas such as "" and "[date]" with your information.
The [cause] has always been very important to [me/ my family]. I have personally experienced how [cause] can affect people when I [where/how experienced issue]. I know that there are over [estimated number] individuals in our community suffering from [related issue]. Your organization's work can provide those individuals, and their families, with the help that they need.
I have decided to financially support your organization this year. Enclosed, you will find my donation in the amount of $[amount]. I [would appreciate/ do not require] a receipt. If you have any questions, feel free to contact me at [contact information].
Please keep me updated on your organization's latest events and progress.