CREST was developed for NREL by Sustainable Energy Advantage (SEA). NREL was seeking a tool that was very flexible, really easy to use, and was able to incorporate the wide array of federal and state incentives currently (or not) available to RE project deployment—not an easy task. SEA conducted a thorough review of publicly available models and cherry-picked the best features. For those who find NREL's System Advisor Model (SAM) too complex for their analysis needs but still want an analytically robust levelized cost of energy (LCOE) tool, CREST may be a good option for you.
The CREST Solar model is available: http://financere.nrel.gov/finance/webfm_send/43/NREL_CREST_Solar_version1.1_Protected.xlsx