I am using the following default file extensions in most of my simulations:

• ras spike raster file (human readable) as produced by SpikeMonitor
• spk Binary spike raster file written by BinarySpikeMonitor (decode with aube or Python tools)
• wmat Weight matrix file (human readable) in Auryn matrix market compatible coordinate real format can be exported and imported by any SparseConnection object
• wmat.cstate In some older simulations an aditional wmat file to storing complex matrix states
• syn Time series file of synaptic weights in human readable format
• mem Default extension for time series files (human readable) with membrane voltage as written by VoltageMonitor
• pat Pattern file (human readable) as can be imported and understood by StimulusGroup, WeightMonitor and PatternMonitor
• netstate binary file storing network state as output or loaded by Auryn kernel
• prate time series (human readable) with population firing rate as written by PopulationRateMonitor
• pact Pattern activity time series file (human readable) computes and monitors population firing rates in neural subpopulations. Produced by PatternMonitor