Kevin Smokler has a fun meditation on the word pulchritude over at his guest blogger stint at Powells.com (he likes the word because it sounds nothing like what it means. "Pulchritudinous" is even more wonderfully dissonant, I think.)
Kevin asks "What are some other words that don't sound like what they mean?" I can't think of any off the top of my head, but I remember that Natalie Goldberg, in one of her books--Wild Mind, maybe?--mentions how beautiful she finds the word "bulimia", even though the meaning is not so lovely. The syllables do roll fluidly off the tongue (which, I suppose, is strangely appropriate!)
My favorite words--luscious and luminous--sound exactly like what they mean, at least to my ears.
I suppose agapanthus sounds more like a disease than a flower, and bilirubin sounds more like a real estate agent than a product of blood...