Kunos Simulazione just revealed a press release containing information that a release of Assetto Corsa is imminent. Because of some issues the company had to change their strategy but the job will be completed soon.
Assetto Corsa will be available on Steam Early Access very, very soon. The game will cost 34,99 Eur (allowing to save 22% of the retail price!) and will give you access to the beta version, including its updates, plus the final version.