Abstract: A natural optimization model that formulates many online resource allocations and decision-making problems is online linear programming (OLP) where the constraint matrix, along with the objective coefficients and decision variables, are revealed and decided column by column sequentially. We review the near optimal algorithms and theories for solving this surprisingly general class of online problems under the assumption of random order of arrival and/or iid distributions of the input data. Then we present few recent applications of the model/algorithm, including a fast online algorithm as a pre-solver for solving large-scale offline (binary) LPs, an interior-point online algorithm to address “fairness” for resource allocation, and a provable logarithmic regret bound for the Bandits with Knapsacks (BwK) problem.