Need an excuse to create a pithy-but-impassioned charitable appeal? How about the chance to attract a $100,000 donation?

Hugh Jackman, the Australian actor, recently put this pledge out on the Twitter Web site: “I will donate 100K to one individual’s favorite nonprofit organization. Of course, you must convince me why by using 140 characters or less.”

Readers are asked to “tweet” their appeals on the Twitter site, where 140 characters is the limit for all communications entered. Appeals have already come in for a diverse group of charities, including Habitat for Humanity, a dance group in Iowa, and an organization that fights anti-gay bullying in schools.

Though an end date for this “tweet for a cause” contest has not been named, Mr. Jackman has suggested it could be April 24

“Your suggestions have been informative, touching and inspiring,” Mr. Jackman wrote as a follow- up. “Please keep them coming. You are educating thousands by sharing your causes.”

“This is a great exercise in being laser-focused, concise, and compelling,” writes the fund raiser Sandy Rees, on her Get Fully Funded blog. “It sounds easy at first, but once you start working on it, you’ll see how difficult it is to work with only 140 characters (for those who don’t know, a character is a letter or a number or a space or a punctuation mark).”

Are you using Twitter in your fund raising? (Read advice from charity experts who already use the tool.)