This letter should be sent to a group of supporters of a cause to inform them of a rally or other protest gathering.
1234, Main Street
Boston, MA 02123
05 April, 2005
<Recipient Address Goes Here>
It's time to take concrete action to fight <opponent you're fighting>. To that end, there will be a <generic name of event> <date and time> at <location>.
We are contacting the local news media, and hope to attract a great deal of publicity to our cause. Please come to the <generic name of event> and show your support for <thing you're trying to save>. And bring a friend.
See you there!
encl: <List of enclosed items goes here>