Observations of the redshifted 21cm line of neutral hydrogen have the potential to probe the processes of structure formation and reionization in a unique way, complementing other techniques in cosmology. The high redshift means that observations have to be done at frequencies of 200 MHz and below, a requirement that presents interesting challenges. First-generation experiments are under construction and will be our first venture into this new area of study. If the challenge of subtracting astrophysical foregrounds can be met, even the modest collecting areas of the first-generation experiments should be capable of detecting the power spectrum of density fluctuations and possibly the largest ionization "bubbles" around quasars. I will present the status of one of these experiments, the Murchison Widefield Array, and discuss possible future approaches to an instrument with greater sensitivity.