From Halopedia, the Halo wiki
Halomaps.org is a website dedicated to hosting custom maps for Halo: Custom Edition and Halo 2 for Windows Vista. The site is owned and operated by UXB Internet, a website design and hosting company with additional company sponsorships and donations.
Started in July, 2004, the site hosts an excess of four thousand maps and files and has distributed over 1,364 terabytes worth of data as of March 2016. The site serves as a popular hub for map-makers and modders. Interaction between users of the site is done through the forums, allowing each and every user a chance to discuss about their map idea and how to successfully compile a working custom map.
The site also features other downloadable contents such as utilities for map-making, tutorials and fan-made videos.