Suspensions of dipolar colloidal particles have attracted recent interest for their highly tunable properties and potential applications as ferrofluids, storage media, and display devices. Modern synthesis techniques enable fabrication of microspheres with permanent or induced electric or magnetic dipoles. Directional interactions between dipolar particles favor complex chain- and ringlike structures, which are observed in experiments and simulations. External fields that couple to the dipoles compete with interparticle interactions and can modify thermodynamic phase behavior. After a brief introduction to dipolar colloids, I will describe an ongoing simulation study of melting in quasi-two-dimensional monolayers, in which the dipoles can rotate in three dimensions. A uniform external field, applied normal to the monolayer, stabilizes a crystal against melting. Spatially varying fields can produce high-resolution patterns in monolayers of bicolored particles -- a scaled-down version of current electronic-ink display technology.