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This paper is a brief tutorial exposition of some recent developments in the evaluation of the reliability of partially-redundant (k-out-of-n) systems. A novel contribution of the paper is that it identifies many practical examples of such systems, which are spread across a wide spectrum of engineering disciplines, including, in particular, the areas of computer and telecommunication engineering. Some formulas for the reliability and life expectancy of these systems are discussed in the case of equal-reliability components. Certain celebrated formulas are shown to be numerically unstable and totally useless in the case of large systems with high-reliability components. In fact, these formulas are highly susceptible to round-off errors and severely suffer from catastrophic cancellations. The paper also reviews how the Boole-Shannon expansion (or equivalently, the pivoting or factoring technique) is used to derive pertinent recursive relations, leading to a highly efficient algorithm for k-out-of-n reliability evaluation. This algorithm has a nice interpretation in terms of a regular Mason signal flow graph, which turns out to be (a) a reduced ordered binary decision diagram representing a monotone symmetric switching function, and (b) analogous to the minimal circuit realization of this function. In the worst case, the temporal and spatial complexities of this algorithm are shown to be quadratic and linear, respectively, in the number of system components. The paper lists some extensions and applications of this algorithm and compares it with a few related algorithms. The paper concludes with a quick consideration of some important issues in the area of k …