It has been almost three decades since Feynman showed that a quantum computer is required to efficiently 
simulate a quantum system.  While building a quantum computer remains a grand challenge, recent advances
in the control of quantum systems have led to a resurgence of interest in quantum simulations.  In addition to 
providing insight into quantum phenomena, quantum simulators could help tackle problems in diverse areas 
such as condensed-matter physics, cosmology and quantum chemistry.  Many quantum simulations require a 
more limited degree of control compared to a quantum computer.   In this talk I will discuss how to build quantum 
simulators using nuclear magnetic resonance (NMR) techniques.  While we can perform any small-scale 
simulation using liquid state NMR, the highly-coupled spin networks in solids allow us to perform a more limited 
set of large-scale analog quantum simulations.  I will illustrate these ideas with experimental examples, and 
discuss the key challenges to developing large scale, general purpose quantum simulators.