NOAA has a new site for distributing charts in the ENC format.
Support for this format is not yet widely available in professional
quality navigation software but is sure to follow in the future. Best
of all, the price is right since we've already paid for it. I've
always been galled by the sweetheart deal that Maptech got from the
gov't with their overpriced BSB charts, paid for by our tax $$$$s.

http://chartmaker.ncd.noaa.gov/mcd/enc/resource.htm