Pope Benedict XVI is now on Twitter
@Pontifex

Vatican Communications (PCCS) confirms this:
https://twitter.com/PCCS_VA

Actually, the Pope has several accounts in different languages, and each is the official Vatican-confirmed Twitter account for the Pope. He is scheduled to answer a few questions by twitter during his general audience on Dec. 12th, 2012.

To follow the Pope on Twitter:

First, you need a twitter account. Sign up (or log-in) at:
https://twitter.com/

Then go to:
https://twitter.com/Pontifex
and click the Follow button

The Papal twitter accounts in other languages can be found here:
https://twitter.com/Pontifex/following

To submit a question to His Holiness Pope Benedict XVI,
tweet the question from your Twitter account, and include:
#askpontifex
in the text of the Tweet

My twitter account is:
https://twitter.com/RonConte