Color (g, r and i band composite) images from the SDSS alongside 21 cm H I line spectra of galaxies clearly detected at Arecibo. The size of each image is 2′ × 2′ with the NIBLES source number indicated in the upper left corner, absolute z-band magnitude, M_z, in the top center and log(M_HI/M_⊙) in the top right corner of each image. The vertical axis in the spectra is flux density in mJy, the horizontal axis is heliocentric recession velocity (cz) in km s⁻¹. The SDSS recession velocity is denoted by a vertical dashed magenta line, the mean H I velocity by the blue triangle, and the W₅₀ line width by the horizontal blue arrow bar. Velocity resolution is 18.7 km s⁻¹. Confused galaxies are denoted by a C in the upper right portion of the spectrum. See Paper II for codes used in the previous campaigns.