  I discuss recent HST observations and interpretation of low-z Ly-alpha clouds
toward nearby Seyferts and QSOs, including their frequency, space density,
estimated mass, association with galaxies, and contribution to Omega_b. Our
HST/GHRS detections of 73 Lya absorbers with N_HI > 10^12.6 cm^(-2) along 11
sightlines covering pathlength Delta(cz) = 86,000 km/s show f(>N_HI)
proportional to N_HI^(-0.6 +/- 0.2). A group of strong absorbers toward
PKS~2155-304 may be associated with gas (400-800)/h_75 kpc from 4 large
galaxies with low metallicity (<0.004 solar) and D/H < 2 x 10^-4. At low-z, we
derive a metagalactic ionizing radiation field and Lya-forest baryon density
J_0 = (1.1 +/- 0.4) x 10^(-23) ergs/cm^2/s/Hz/sr and Omega_b = (0.008 +/-
0.004) h_75^(-1) [J_-23 N_14 b_100]^0.5 for clouds of characteristic size b =
(100 kpc)b_100.
