Here is a partial list of interesting practices I’ve seen, which I can compile into an internal or external wiki if I don’t come across an existing repository yet:

• Voting buttons in newsletters to allow people to rate the usefulness
• Subscription button in newsletters to allow people who received forwarded messages to be added to the distribution list
• Calendar buttons
• Forms/surveys
• RSVP+calendar entry buttons in event invitations – creating non-blocking entries if necessary
• Calendar button for scheduling replays if you can’t make it to the original event
• Using sections to hide material (note: manually configure section properties so that sections are collapsed by default, but automatically expanded for printing)
• Voting/volunteering buttons
• Response summarization agents
• Mail merge
• Stationery
• Standard response documents
• Introductory sentence explaining why people are getting mail
• Reply button with template