If you're in fundraising, you're in the direct mail business. So it would serve you well to read up on what for-profit and not-for-profit direct mail professionals are learning. They are constantly testing and retesting the effectiveness of each package.
One of the ideas I've heard over the years is that signing letters using blue ink elicits a better donor response.
Blue ink seems to be one of those "facts" that everyone seems to refer to but few actually have cited the research. (Google Answers does have some studies that back this up.)
Like everything in direct mail, you'll need to test this out for yourself. Any tests that show something lifts response rates is tested with a specific package, for a specific organization, at a specific time. Your context may be different.
But isn't there something wonderfully alive about seeing a blue name at the bottom of a printed black letter? Even when you know your's is simply one merged document of the thousands that got sent, it seems more worthy of attention.
And there's something that connects better when you receive a handwritten note in blue ink rather than black. I'm not sure why, perhaps black ink reminds us of computer printed form letters.
In our day of color printing, it's even possible to print a blue signature AND a blue handwritten P.S. on mass produced letters.
Blue is still professional enough for the conservative types (those that may get thrown off by "fuschia" or "mauve"). But the touch of color brings life to everything from a direct response piece to a handwritten note.
It's so simple. Why not try using blue on your next letter and test the response?