The site every person living with bipolar should read and have their loved ones view.

http://www.blackdoginstitute.org.au/index.cfm

I feel like this would be a good tool to inform people you know about the disorder if/when you tell them. There are many misconceptions about bipolar, this site gives it to you straight (There is NO CURE, but you can manage it and be happy. Here's how.) Even has educational videos from professionals and experts, many of who have been diagnosed.