There are several ways to share your maps with friends:
1. If your map is public, you can just send them a link to the map page by email or post to your facebook wall using the [EMBED] button under the map
2. If you don't want to make your map public, you can set the map to visibility "friends" and it will be visible to any of your friends that already have Tripline accounts
3. If you want to keep your map private and only share with a small group of people, go to the map page and click [ADD PEOPLE] on the right side just below the map. You can add Tripline friends, Facebook friends (if you've connected your account to Facebook) and invite by email. You can also choose whether to add people as travelers or followers. In either case, people you add will be able to access your map as soon as they create a Tripline account and accept your invitation
We've had a number of requests to offer simple password protection that would you allow a keep a map private and just send people a link and a password. That's in our feature queue so hopefully we'll be able to get it done at some point soon.
In the meantime, get your friends to sign up with Tripline! That makes everything easier and helps us too :)