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In order for cognitive radio systems to fulfill their potential of enabling more efficient spectrum utilization by means of opportunistic spectrum use, significant advances must be made in the areas of spectrum sensing and “cognitive” spectrum access. In this paper, we discuss two research efforts relevant to these areas; namely the development of distributed (cyclic feature-based) spectrum sensing algorithms and of available resource maps-based cognitive radio systems. It is shown that distributed spectrum sensing is a practical and efficient approach to increase the probability of signal detection and correct modulation classification and/or to reduce sensitivity requirements of individual radios. Additionally, numerical results are presented that show significant reduction of harmful interference and greater spectrum utilization efficiency of available resource maps-based cognitive radio systems.