Community Map Pack
The ACMP was a download-able pack that included many high quality maps that aren't in the official download packages. These maps weren't modified in any way. There were over 50 quality maps in this map pack as seen at the included maps page.
This was maintained by R4zor, and updates were stopped around the 1.1 release.
The MAP PACK!
The MAP PACK! was a planned developer-produced pack (RandumKiwi) that players could download to easily get a collection of quality maps, that was separate from the official download package.
The pack has never been officially released. The original post about the pack was lost.