Festival programmers said global submissions grew by 15% over last year as they sifted through 5,107 hopefuls from 17 countries.
Dunst arrives in the US Short Films programme with Welcome, which stars Winona Ryder in the tale of an ultimately friendly spirit that inhabits a family's new home.
In the documentary section Rossellini's Green Porno comprises a collection of ultra-short films about the sex lives of insects.
Murderball director Dana Adam Shapiro's My Biodegradable Heat in the Animated Shorts line-up centres on puppy love and looks at how long it takes for said puppy to decompose.
For the first time Sundance will make the shorts available for purchase on iTunes, Xbox LIVE and through Netflix.
'Since the beginning we recognised short films as a viable art form and an exciting way to discover and launch new talent,' Sundance's director of programming John Cooper said. 'We will continue to find innovative ways to extend the success and reach of this amazing work and build a worldwide audience for short-form films.'
Sundance runs from January 17-27 2008. For the complete line-up visit www.sundance.org.