In Outlook you can drop an email onto a Calendar icon to create an event. It's one of Outlook's better features.
Toodledo customers get an email connection for task creation. Send an email and Toodeldo creates a task. There are even rules for writing subject lines to facilitate task creation.
Unsurprisingly, Google has something similar - albeit with a bug that makes it less useful than you'd think.
The SMS submission feature is poorly documented; before you can use it (US only) you must register your phone using the Calendar Settings Mobile Setup tab. It worked in my testing, I received a confirmation email that the event had been created. The SMS submission feature, and some related SMS calendaring services, are most useful for non-smartphone users. I think it follows the same language recognition rules as email (below):
There's no exact email analog  to the SMS feature, but Gmail processing comes closes. You can create an event from any email; the secret is the More Actions drop-down menu and the Create Event entry (I need to pay more attention to that menu!).
Google Calendar tries to parse the email subject line to set times and dates for the new event. I couldn't find any documentation on what phrasing works best, but I assume Google uses the same rules as the "Quick Add" entry box in Google Calendar ... (rewritten below, the page is a mess).
If you're sending an email to your Google Account to facilitate event creation you should use the following rules tge recipe for events is to enter 'what,' 'who,' 'where,' and 'when'. I can't remember that, I prefer the acronym SNAD:
- Subject (what): This can be any text; the event title is created from this.
- Name (who, optional): Anything preceded by the word "with".
- Address (where, optional): Preceded by the word "at", use quotes if the place name could be confused with a date/time.
- Date (when): Preceded by the word at. Almost anything will work, colons in times can help reduce ambiguity and military time works.
The classic example is: "Dinner with Michael at "Friday's" at 7pm tomorrow".
So far, so good -- but there's a nasty bug/limitation. When you use the create event feature in Gmail, you can only create it on your personal calendar -- even though you may have privileges to write to many calendars. After you create the event you can move it the correct calendar.
 Don't confuse this with what happens when you send an invitation to a Gmail account for an Outlook or similar appointment. That sends an ICS attachment and, think it automatically creates a calendar entry.