If you join the
Arbor Day Foundation (6 month membership is $10), they'll send you 10 free (small) trees.
Another way - (found online a long time ago - don't know what the budget crisis has done to these programs) "Many cities offer free workshops after which they’ll give you a free tree to plant in your yard because it has a positive aesthetic effect and even energy-saving potential down the road. The City of Los Angeles offers one such shade tree program, hoping to turn around its reputation for being an ungreen city of smog. Other cities that offer free tree programs include
San Diego and Columbia (MO). Often, these tree giveaways are not well-promoted online, but a few phone calls to your alderman or to a city hotline can direct you to the right department."
(And welcome to VALGAL
)