No easy way, just select up to 100 of your friends as to,cc,or bcc and send. If more than 100, you will have to send multiple messages. Depending on the interface you use (webmail, Outlook, Thunderbird, etc.) it may be easy or hard to select multiple users at the same time.
See if you can open your address book, and select the first and shift select the last (remembering the limit of 100) and then write an email