MAPS AND RMSesThis thread will be a big list of scenarios and random maps you can add to your games of 0AD; there are install instructions for new maps & scenarios at the bottom of the first post.
ScenariosJubal's Maps:
http://www.exilian.co.uk/forum/index.php?topic=1078.0Yodaspirine's Maps:
http://www.wildfiregames.com/forum/index.php?showtopic=13630idanwin's Black Island:
http://www.wildfiregames.com/forum/index.php?showtopic=16919Sanderd17's Hadrian's Wall:
http://www.wildfiregames.com/forum/index.php?showtopic=17342Sheesania Maps Page:
http://sheesania.com/s/0-a-d-maps/To Install ScenariosGo to your 0AD folder, then go binaries -> data -> mods -> public. Then unzip public.zip, go to maps -> scenarios in the new unzipped file structure, and paste 'em there then unzip. You should be able to reach them ingame by selecting "All Maps" under the map filter when starting a game.
On Ubuntu, your 0ad folder will be buried in /usr/share/games/0ad. It won't have the maps/scenarios folders, so open up Nautilus as root (Alt+F2, gksudo nautilus) and enter your password, then navigate to /usr/share/games/0ad/mods/public and create a folder called 'maps' (without quotes) then inside that make one called 'scenarios' (without quotes). Then put your map files in there, and access them the same as above.
To Install Random MapsThe random maps work very much as above except instead of the "scenarios" folder it's the "random" folder you want.