Fast electronic motions are important in photochemistry, photosynthesis, interfacial electron transfer, and in some proposed next-generation photovoltaics. In 1998, our group used femtosecond lasers to demonstrate the first optical analogs of early two-dimensional NMR experiments. Our approach is now widely used to measure fast electronic and vibrational motions in disordered environments such as liquids, proteins, and semiconductors, but more work is needed to develop 2D spectroscopy as an analytical technique. We have used 2D femtosecond spectroscopy to probe the fastest electronic motions within molecules, the vibrations coupled to those motions, and the coupled motions of the environment. Topics of interest include electronic dynamics at "conical intersections" between electronic potential surfaces, surface-enhanced Raman scattering on metallic nano-particles, high-efficiency electronic energy transfer, hot carrier dynamics in semiconductor quantum dots, and other approaches to higher efficiency solar energy conversion.