What other really hardy palms are available?

The following species are quite cold hardy, to around -10°C (14°F), some a little more: Brahea armata, B. decumbens, B. dulcis, B. moorei, Butia capitata, B. eriospatha, B. microspadix, B. paraguayensis, B. yatay, Chamaedorea radicalis, Chamaerops humilis, Phoenix dactylifera, P. theophrastii, Sabal etonia, S. mexicana, S. palmetto, S. uresana, Trachycarpus latisectus, T. oreophilus, T. martianus (Nepal form), T. princeps and Washingtonia filifera.