Radio telescope arrays for NEO search.
Your question about the Allen Array which is actually intended for SETI search reminded me of the planned Square Kilometer (or Kilometre) Array, SKA. It's planned to be operational by 2012. It's intended to increase the sensitivity of current radio telescopes by a factor of 100. One of the intended purposes is to be used for a search of NEO's.
With the planned optical telescopes and radio telescopes in the pipeline, I think there is actually reason for optimism in the search for possible Earth impactors:
Solar System Science with SKA.
http://arxiv.org/abs/astro-ph/0409220
Bob Clark