Here are the refereed proceedings of the EUC 2006 workshops, held in conjunction with the IFIP International Conference on Embedded and Ubiquitous Computing in Seoul, Korea, August 2006. The book presents 102 revised papers spanning six workshops: network-centric ubiquitous systems (NCUS 2006), security in ubiquitous computing systems (SecUbiq 2006), RFID and ubiquitous sensor networks (USN 2006), trustworthiness, reliability and services in ubiquitous and sensor networks (TRUST 2006), embedded software optimization (ESO 2006), and multimedia solution and assurance in ubiquitous information systems (MSA 2006).