Fastmap is a HTTPD plugin that allows for the transfer of the BZW map file over HTTP instead of sending it through the game client. Sending it through the client is limited to 1kb per lag time, which causes large maps to take a long time to download. Fastmap automatically sets the map's HTTP url to the server, allowing for a much faster download of the map file (hence the name, Fastmap).
The plugin requires the HTTPServer plugin to either be in the same directory as fastmap.so, or to be previously loaded. Unlike other HTTPD plugins, Fastmap does not create a vdir.