Arak-Athor is a subsistence barren planet located in the middle of the Patch Nebula. A large space station Barzoom, orbits this planet at all times. This station is the headquarters of the Shadows of Midnight crime syndicate. Yorba-gunn the crimelord who rules this station lives in here.
The Mon Calamari homeworld is described briefly on Galaxy Guide 4 - Alien Races (pp 67-68). Calamari is a water world, most of the surface is covered with water, with a few islands and small continents. These islands and small continents have lots of lakes and marshes in them. Calamari is the only rebel alliance controlled manufacturing facility of capital ships, and dockyards.
18) Re Albi
Re-Albi is a mining planet with lots of caves. Located on the western edge of the sector, this planet and the other four in the system are controlled by twelve mining corporations, ruled by very powerful families. The empire has a major garrison on Re-Albi.
All the planets in this system are dedicated to the mining industry. A lot of the ore used by the empire in the shipyards or in other facilities is mined in this system.