Building efficient internet-scale data management services is the main focus of this chapter. In particular, we aim to show how to leverage DHT technology and extend it with novel algorithms and architectures in order to (i) improve efficiency and reliability for traditional DHT (exact-match) queries, particularly exploiting the abundance of altruism witnessed in real-life P2P networks, (ii) speedup range queries for data stored on DHTs, and (iii) support efficiently and scalably the publish/subscribe paradigm over DHTs, which crucially depends on algorithms for supporting rich queries on string-attribute data.