Much of the success in optical quantum computing and quantum key distribution has come from linear techniques, in part due to the difficulty of developing systems which exhibit optical nonlinearities at low photon numbers. Hollow-core photonic band-gap fibers, when filled with Rb vapor, provide a system with strong coupling to resonant light. This opens the door to a variety of interesting quantum-optical experiments where low-photon number states can induce measurable nonlinearities, and where moderate amounts of light can produce unusually strong nonlinear effects. I will present recent experiments in our Rb-loaded fibers on electromagnetically-induced-transparency in the presence of buffer gas, four-wave mixing with gain >100 and bandwidths >300 MHz at
microwatt power levels, and all-optical switching with a few thousand photons, as well as some thoughts on future directions.