It won't happen again until December 2117. On June 5th, 2012, Venus will transit the face of the sun in an event of both historical and observational importance. The best places to watch are in the south Pacific.
On the www.sunaeon.com it is available a cool animation of the tranist.
Videos and pictures of the transit will be broadcast live on the venus-2012.org from Australia (Cairns), Japan (Sapporo) and Norway (Tromsø).
Furthermore the free app VenusTransit made by Astronomers Without Borders allows users to find out when and where the transit will be visible, follow transit-related tweets, download photos and videos and learn about the history of the transit. The app is available at iTunes App Store and Android Market.