(Gliese 581d photo courtesty of ESO.)
Hello From Earth is a Web site that has been set up to mark National Science Week in Australia. The site is allowing registered users to send English-language messages of up to 160 characters to Gliese 581d, a planet believed to be about eight times heavier than our own and located more than 20 light years away in the constellation Libra. The service is free and will be available until August 24, 2009.
Note that it will take 20 years for the messages sent via satellites into deep space from the Canberra Deep Space Communication Complex to arrive.
Will you send your potential neighbors an invite to visit in 2029?