Kids love music and research has also shown that music helps kids learn. So invite some other toddlers over and have a jam session. Ask each child to bring a special “instrument” (rattle, drum, etc.). Find some fun cds from the library and when everybody arrives have them march around the house/room playing to the music.
For an added activity, find a picture book from the library that shows all the different kinds of instruments and try to have the kids find their instrument (the one they brought with them) in the book.