PROBLEM: You have organized your friends into specific lists like high school, family, football, etc. and you want to send one of those lists a message.
SOLUTION: As of October 2, 2012, there is now way to do this. The friends lists are next to useless you want to keep track of their statuses. The only way to do something similar to do this is to create a Facebook page and invite those friends to LIKE the page. Then you can send a message to everyone who liked the page. However, Facebook doesn't like frivolous pages, so we are all stuck in a kind of Catch 22.
WHY: My theory is Facebook is trying to stop people from spamming large lists of people.
ADDITIONAL SOLUTION: Manually enter everyone's name on a message. Keep in mind this opens a conversation, so if somebody responds, everybody esle will see the response.