It is very problematic to provide examples of fundraising letters. They vary tremendously, depending on the nature of the charity, the resources that charity has to apply toward direct mail fundraising, and the creativity of the person who writes that letter.
In addition, the letter is just one part of a complete direct mail package that can include brochures, the envelope carrying the letter, the reply envelope, the reply device, premiums, and sometimes much more.
Nevertheless, I've collected some actual fundraising direct mail letters and present them here, without their accompanying packages. These are letters that I think work well, but use them with care. They might be totally wrong for your needs. Only use them as inspiration for your own copywriting endeavors.
Start with Top 8 Tips for Writing a Fundraising Letter
Index of letters: