I just found today a great tool called Twittercal. http://www.twittercal.com

With this tool, you can simply send a message to a twitter account and it will post an appointment on your Google Calendar.

I have Outlook syncing with my Google Calendar. I have an iPhone that is linked to my Outlook. So from any calendar or from Twitter I can set appointments.

First, you sign up for a twittercal account. (Actually, you are creating a link between your twitter account and gmail account.)

You then follow gcal (a twitter user), and from then on you send your appointments via a twitter post such as:

“d gcal Appointment with Sophia at 7pm tomorrow”

d stands for a direct message, gcal is the user you are sending the message to, and finally the appointment description and time.

Within a minute or so, it automagically appears in your Google Calendar.

Give it a try!