Once you have your edited movie ready to go, choose Share from the Menu Bar and choose one of the following:
Export Movie: This will show you a list of devices that the movie can be sized to work well on
Export using QuickTime: This will allow you to choose what size & type you want, I would suggest Movie to Quicktime and then choose the method by which the finished file will be transmitted & received.
As Bob mentioned, bear in mind that there is a size limit for attachments on email. This varies with each ISP a movie that is 20MB is not likely to make it to the recipients, even if your ISP allowed you to send it.
Bob mentioned a piece of software called Dropbox.
It's free and would allow you to literally drop your movie into the drop box and allow others to access your drop box to download the file.
No mail involved, except for you notifying your friends about how to access your drop box.