requires shapefile-js plus if you want it to be done in a worker, you'll need catiline.
usage:
new L.Shapefile(arrayBuffer or url[,options]);
L.shapefile(arrayBuffer or url[,options]);Options are passed to L.Geojson as is. First argument is either an array buffer of a zipped shapefile, the url to a zipped shapefile, or the url to file.shp (this assumes file.dbf exists).