The properties of fluids near interfaces, in particular, the fluid-solid interfaces on which this work is concentrated, are important in many processes, such as: wettability as related to oil recovery and environmental cleanup, biochemical separation, bio-compatibility of materials, membrane separation, adsorption in porous solids and micro- or nanomanufacturing of thin films. However, little of the past simulation and theoretical work in the field has considered associating fluids. In this work we perform Metropolis Monte Carlo computer simulations for one-sited (dimerizing), two-sited (linear chain forming), and four-sited (cluster forming) hard spheres against hard, smooth walls. Reported are results for density and fraction of monomers (which determines the change in Helmholtz free energy due to association according to Wertheim's theory) versus distance from the surface. Also computed are adsorption and for the four-site fluid, orientation, cluster size, and fraction of sites bonded as functions of distance from the surfaces. We also consider binary mixtures and an associating fluid near active surfaces. Except for orientation and cluster size, results are compared (favorably, in general) against a new density functional theory, which combines elements of the Tarazona density functional for hard spheres and Wertheim's theory of association. This dissertation concludes with ideas for further work in the area.