  The Arecibo Legacy Fast ALFA (ALFALFA) survey is a second generation blind
extragalactic HI survey currently in progess which is exploiting Arecibo's
superior sensitivity, angular resolution and digital technology to derive a
census of the local HI universe over a cosmologically significant volume. As of
the time of this meeting, some 4500 good quality extragalactic HI line sources
have been identified in about 15% of the final survey area. ALFALFA is
detecting HI masses as low as 10**6 solar masses and as large as 10**10.8 solar
masses with positional accuracies typically better than 20", allowing immediate
identification of the most probable optical counterparts. Only 3% of all
extragalactic HI sources and less than 1% of detections with HI mass 10**9.5
solar masses cannot be identified with a stellar component. Because ALFALFA is
far from complete, the discussion here focuses on limitations of past surveys
that ALFALFA will overcome because of its greater volume, sensitivity and
reduced susceptibility to source confusion and on a sampling of illustrative
preliminary results. First ALFALFA results already suggest, in agreement with
previous studies, that there does not appear to be a cosmologically significant
population of optically dark but HI rich galaxies. ALFALFA promises a wealthy
dataset for the exploration of many issues in near-field cosmology and galaxy
evolution studies, setting the stage for their extension to higher redshifts in
the future with the Square Kilometer Array (SKA).
