From the Aussiecon 4 news feed:

Aussiecon 4 received a record number of nominations for the 2010 Hugo Awards: 864, up from 799 nomination ballots at Anticipation in 2009 and 483 at Denvention 3 in 2008. This year’s Hugo Award nominations will be announced 22:00 BST, Easter Sunday 4 April, at Odyssey 2010, this year’s Eastercon, and covered live on the Aussiecon 4 Twitter feed. Balloting for the Hugo Awards will commence thereafter and will conclude on 31 July at midnight, US PDT. The Hugo Awards Ceremony will be held at Aussiecon 4 in Melbourne on Sunday, 5 September 2010.

You can find the Aussiecon 4 Twitter feed here.

For further details about the announcement event, see the Eastercon web site.