A bis-fused TTF donor, 2,5-bis(1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene (TTP) and its derivatives affords many metallic salts stable down to low temperatures, X-Ray structure analysis reveals that most TTP salts have beta-type conducting sheets regardless of counter anions, On the other hand, CH-TTP and TMET-TTP have a tendency to form kappa-type and theta-type salts, respectively. A vinylogous TTP DTEDT has afforded an organic superconductor (DTED-T)(3)Au(CN)(2), and a TTP analog containing thiopyran ring TM-TPDS has yielded the AsF6 salt with three-dimensional molecular array.