The Eragon demo can be downloaded by Xbox Live Gold members only, and weighs in at a reasonable 415MB. The game's in development at Stormfront (LOTR The Two Towers & Forgotten Realms: Demon Stone), and is based on the upcoming 20th Century Fox film, which itself is based on the books by Christopher Paolini.
You play as Eragon, a young farm boy who discovers a dragon egg and goes on to become a Dragon Rider. After his parents are killed by the dark forces in the kingdom, Eragon and his dragon Saphira set out to bring peace to the realm.
Eragon is scheduled to arrive later this month for Xbox 360, PC, PS2, PSP, Xbox, DS and GBA.