Major Nelson has reported that the new Halo 3 Map Pack has now hit Xbox Live along with some extras, the full details for those interested in buying this are below courtesy of the man himself.

Content: Halo 3 Legendary Map Pack
Price: 800 Microsoft Points
Availability: All Xbox LIVE Regions
Size: 411.34 MB
Dash Text:[ESRB: M (Mature) BLOOD AND GORE,MILD LANGUAGE,VIOLENCE] The Legendary Map Pack blends old and new. Ghost Town’s asymmetrical mix of confined spaces and long lines of fire makes for frenetic games. Avalanche re-imagines the original Halo classic, Sidewinder, with new features, tweaked vehicles and massive outdoor spaces. Significant changes bring big improvements to the map, yet its contours and cliffs should provide a welcome sense of familiarity. Blackout, on the other hand, is the purest remake to date – all time favorite Lockout gets a graphical overhaul, but retains its challenging mix of ramps, platforms, tunnels and hallways. There are no refunds for this item. For more information, see www.xbox.com/live/accounts.

Plus:
Content: Halo 3 Legendary Map Pack Dash Theme
Price: Free
Availability: All Xbox LIVE regions
Dash Text: Time to spruce up your Xbox Live Dashboard theme with this brand new, Legendary Map Pack-inspired theme, featuring images, moments and atmosphere from the latest batch of Halo 3 DLC. The Human industrial grit of Blackout, the wintry vastness of Avalanche and the gloomy ruin of Ghost Town will be a welcome aesthetic boost for fans of Dashboard themes.