Google Drive has added a new sharing option that instantly creates a URL you can share with others without having to specify their email address.
The Share button (found in the top-right of every document in Google Drive) now includes a new "Get shareable link" option. That link will be view-only by default. You can alter it to allow editing, but bear in mind that without specifying individual users, anyone who gets hold of the link will be able to make changes.
As with many Google updates, this one may take a few days to appear on your account (it hasn't shown up on mine yet).
Sharing just got a little easier [Google Drive]