Fast forward to 2022.
The MBTA now officially charges USD 3.00 for a (plastic) Charlie Card although there are a few circumstances when you can get the card for free.
The MBTA is in the midst of revamping the fare structure and rules, so many of the points in preceding replies have changed. They call it Charlie 2.0 and it involved replacing all of the fare gates and all of the fare vending machines.
Some other highlights:
When buying tickets to ride the subway, do not select "commuter rail" on the touch screen.
Taking the tunnel bus (Silver Line) from Logan Airport to downtown, boarding and connection to the subway is free for that first ride (subject to change without notice). But there can be numerous delays due to traffic. If you take the airport shuttle bus to the Blue Line rapid transit about a mile away,, you pay the normal fare at the Airport station.
Charlie tickets with magnetic (black) stripes are no longer valid anywhere although value can be transferred at the Charlie Store (just one location observing bankers' hours at the Downtown Crossing station outside paid area). New style Charlie tickets with touch sensing (RFID) are now in use.
An overall fare increase (a few fare categories have a decrease) is effective July 1, 2022.
All along, Charlie cards have been handed out at random stations at random times; otherwise only (paper) Charlie tickets were available from fare vending machines.
Every now and then a plastic Charlie Card is found including in a wastebasket. It is dangerous to pick up and use it because some Charlie cards are owned by corporations for their employee fare plans and the card could be invalidated without warning. But you can get away using a found card for small amounts of fare.
Last edited by AllanJ; Jun 26, 2022 at 7:29 am