The most important feature of Google Docs is collaboration, but it's not very easy to manage the list of collaborators or to use it for other documents and outside Google Docs. One small feature that will help if you have a lot of collaborators is the possibility to create a Google Calendar event that invites everyone working on a document.
This only works for shared documents and lets you create events that includes all the collaborators and invited viewers as guests. The invitation also contains a link to the document and the collaborators don't have to use Google Calendar. "Anyone with an email address can receive invitations from Google Calendar. When your guest receives an invitation email and clicks on one of the attendance options, he'll be taken to the event page where he can check other guests' attendance status and he can leave comments."
It's easier than manually copy-pasting email addresses and Google Calendar keeps track of those who accepted the invitation, so you don't have to. "This feature is great for those of us who enjoy Google Docs & Spreadsheets as a collaborative resource for collaborative events -- think of all the times a document becomes a meeting -- scheduling a get-together to review a proposal, sending an agenda in advance, or just keeping score for your Wednesday night backgammon club," suggests a Google Docs guide.