We present x.qui.site, a scalable system for managing recommendations for social tagging sites like del.icio.us. seamlessly incorporates various user behaviors into the recommendations and aims to recommend not only items of interest, but also other relevant information like interesting people and/or topics. Explanations are also provided so that users can obtain a better understanding of the recommendations and decide which recommendations to pursue further. We discuss the technical challenges involved in characterizing different user behaviors and in efficiently computing recommendation explanations. Categories and Subject Descriptors H.4 [Information Systems Applications]: Miscellaneous General Terms Algorithms Keywords Tagging, Collaborative Filtering