Everything Touhou music related is listed here.
The Touhou Project is a series of shooting games, with four fighting game spinoffs.
The music in Touhou is popular and has been rearranged and remixed numerous amount of times and included in music videos. Many arrangement CDs can be found for sale at Comiket, and there are music circles dedicated to remixing Touhou music. For example RegaSound (with Rumdarjun).