This paper presents research on citizen-centered smart services from the perspective of a long-term project. Initially intended for E-Government services in social, economic and biological domains, it is naturally extended to smart city services due to the common goals of citizen-centered services, common data sources, similar technologies, and the like. It is also overlapped with some international cooperation with similar goals. Both, E-Government and Smart Cities, feed with information that originates from their sensors, citizens and IoT, and, in return, provide smart services that aim to improve the quality of life and achieve more efficient management in the different environments in which they operate. The sensing is provided by listening to citizen opinions via social media, like Facebook, X (formerly, Twitter), and the like, and other Web 2.0 methods like crowdsensing and crowdsourcing, etc. The emerging world of IoT allows to sense some environmental phenomena like temperature, air pollutants, traffic congestion, fire, flooding, and to evidence some illegal behavior on the streets, for example. Development and deployment of citizen-centered services are analyzed through the prism of four dimensions, namely (1) modeling and decision-making, (2) sensing and analyzing, (3) willingness and engagement, and (4) openness and transparency. In addition, key technological enablers that drive the full achievement of these dimensions are briefly discussed. To address the challenges several issues are discusses. These include the enormous amount of data with high velocity, value and variety, the complexity of Serbian language and grammar with the absence of linguistic resources, and the limitations of IoT resources, to mention a few. These challenges are discussed by related work and a brief overview of proposed solutions with special emphasis on a framework, design of several specialized social machines, text processing in Serbian language, sentiment analysis, business process management and an excerpt of developed and deployed services. We briefly outline the main contributions of published work, including the key and technologies utilized, all supported by several experimental results. We conclude by identifying some unresolved problems and proposing future research directions.