Excellent links - thank you. I appreciate sources that don't go hyperbolic about toxicity or that are trying to sell the product. One of those pages mentioned Vieth who has been maintaining for several years now that the current RDA's are too low. Here are two journal articles that discuss the topic of RDA's and supplementation. The texts are available online.
Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am.J.Clin.Nutr. 1999;69:842-56.
Glerup H, Mikkelsen K, Poulsen L et al. Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. J.Intern.Med. 2000;247:260-8.