import arcpy
from arcpy import env
def loadAllShapefiles(path):
    # set workspace path to the one we will be searching SHPs in
    env.workspace = path
    # get a list of all SHPs in the folder
    fcList = arcpy.ListFeatureClasses()
    print fcList
    # sets mxd to the currently opened document
    mxd = arcpy.mapping.MapDocument("CURRENT")
    # sets df to the first data frame
    df = arcpy.mapping.ListDataFrames(mxd, '')[0]
    # iterates over every SHP name in the folder
    for fc in fcList:
        # get the whole path to the SHP
        pathToFC = env.workspace + "/" + fc
        # create a new layer from the SHP
        newLayer = arcpy.mapping.Layer(pathToFC)
        # add the new layer to the bottom of the data frame
        arcpy.mapping.AddLayer(df,newLayer,"BOTTOM")
        # refresh Table of contents and the active view (so the layers appear immediately when the script finished)
    arcpy.RefreshTOC()
    arcpy.RefreshActiveView()