In my humble opinion, jQuery is more than a javascript library because it has a very specific linguistic style. Needless to say - I'm a big fan!
And though I've been using jQuery for a few years, I've only started to use Ruby extensively during the last year or so. The experience has been terrific, and I'm starting to see some similarities between what I like about the two languages.
I believe these are both essentially anonymous / lambda functions, but I'm still learning the terminology so forgive me if I'm mixing terms.