Old West is a fan-made variant setting of Hollow Earth Expedition using the Ubiquity system. The setting and a few adventures are all available for free at the Mythic Eras website. All of this fine work is written by Ingo Kvalø-Hamann.
Old West (v2.2) - Rules Supplement - A full Old West setting. Everything you need to takeHEXto the wild and woolly West. From character types to Indian mysticism. From gambling to prospecting. You can play it straight or drop in some magic.
El Brujo - Adventure - A dangerous gang of outlaws is terrorizing the area of Southern New Mexico, settlers and ingenious tribes alike. These bandits prey on young women, which they abduct from isolated farms or settlements and sell south of the border as slaves.
Ivory Trail - Adventure - Once upon a time in the Old West, three men robbed a bank and got away with a fortune. But the men started quarreling and finally the two underdogs shot their leader. They took the money and a pair of ivory-handled silver Colts. To avoid suspicion, the two men decides to hide the money and return to their jobs and families, waiting for the right time to fetch their reward. On their flight they stumbled over an ancient artificial cave complex. As the men explored the complex they decided that this would be an excellent place to hide their loot.
A Series of Unfortunate Events- Adventure - Finally, the successful prospector Angus McAvoy made enough money to realize his dream of starting a ranch. With over $50,000 in is wallet, he came to Clearwater, a town in the territory which is known as Colorado, to buy himself a ranch. The future rancher placed his money in the local bank and started to investigate his possibilities. Then a series of unfortunate events began...