I shall present two pieces of recent work from my group. The first concerns electrophoresis of colloidal particles in surfactant-doped nonpolar liquids. Here, experiments over several decades have reported that the electrophoretic mobility (i.e., the particle velocity per unit field) varies with the applied field strength. I will develop a simple electrokinetic model that captures this effect. In the second part of this talk, I present a model for the linear viscoelasticity of a dilute suspension of active (self-propelled) particles. Notably, the model predicts that the particles cause a negative increment to the suspension viscosity. Through a comparison of the model to recent experiments on suspensions of Escherichia coli, I will demonstrate that biophysical parameters of these microorganisms can be inferred from linear viscoelasticity.