i've been using delicious (name: cherzig)for several years now--first as a cataloger, so i have a lot of cataloging sites, then as an electronic resources librarian, so i have some of those types of sites. somewhere along the way i made a personal site but haven't done much with it.
i find social bookmarking to be extremely helpful! i have networked with several other library-related delicious accounts, such as "acclibrarians" and "FWPL". Our reference librarian also made a delicious site for library reference, for staff as well as for the publice. we have a link to it on our web site.