I wanted to clarify my thought process.
#Need to use a for structure so that each input feature class is taken in turn
for each shp in featureclasses:
#Get the name of the feature class
outFeatureClass = os.path.join("C:\GIS\Scripts\temp\temptrks", shp.strip(".shp"))
#Copy and past the feature class to the temporary workspace, to preserve original
#Add filename field to the copy
arcpy.AddField_management(outFeatureClass, "filename", "TEXT", "","", "254")
#Calculate the filename attribute from the file name
#Then append each feature class, probably with another for each It seems a little lengthy, and I'm thinking there's got to be an easier way to capture the filename.