Penn Library does social bookmarking
I saw a link to this in my referrer logs…
It has a feature called projects, which are basically folders for those who aren't folsonomified yet. There also all the goodies you'd expect from commercial social bookmarking sites, such as RSS feeds for everything, bookmarklets and even a Firefox toolbar (for bookmarking and other library tools).
This is the first I've heard of this, but a quick Google search reveals that this is at least 4 months old. I'll be the first to admit I don't spend much time at the libary (Whartonites are averse to any text not in Excel), but this is the first I've heard of it so they haven't done a good job of advertising it.