I have been looking for the shape files for the Bull Shoals Lake, and Norfork lake in Arkansas.

http://water.usgs.gov/GIS/dsdl/ds240/index.html

It is mentioned here :
http://msdis.missouri.edu/datasearch/metadata/utm/st_lake_cls_use.xml
"The following water bodies were included in the NHD and staff edited the polygons with GIS software to more accurately depict the water body.
"
7317 Norfork lake
7315 Bull Shoals Lake

I have used the shp2osm converter here:
http://svn.openstreetmap.org/applications/utils/import/shp2osm/shp2osm.pl

And I have written a filter to extract only water out of those maps :
http://bazaar.launchpad.net/%7Ekosova/%2Bjunk/openstreetmapkosova/revision/100

The import looks good, and I am running it only Bull Shoals at the moment, using a coastline relationship.

If there is interest, we can import more.
osm.org/browse/changeset/3355937