Oh, if it doesn´t sound too "commie" for you, I´d suggest The Internationale, of course. As far as I know, "Joe Hill" is on the DigiTrad Archive, you just have to look for it. "The Red Flag" on The White Cockade Tune; to Tannenbaum it sounds like a funeral march. "There´s power in a union" if you know Billy Bragg. "Bread and Roses" sounds good if sung by a women´s chorus. "This land" by Woody, but you must sing those censored verses at the end. "Union Maid" should sound funny. "Pie in the sky", "Long-Haired Preachers" or whatever you call it, should get some people singing as well. But maybe they´re all a bit extremistic... Well, I like them, but I also think you should try not to scare anyone who´s not used to hear such things...

"Deportees", if you expect Mexican people in the audience. I know people like "Bandiera rossa", you can also just play the tune. Yes, you don´t get too many songs if you post LABOR DAY, but try with LABOR or WORK or SOCIALIST or UNION.

,-) Well, we have the REAL Labor Day on May 1st in Italy. Why don´t you fight to get it back? It´s our right to have fun on that day, and the weather is also usually better.