Hebrews 13:3 (NIV)
Continue to remember those in prison as if you were together with them in prison, and those who are mistreated as if you yourselves were suffering.
Several practical opportunities to live out this scripture can be found at Christian Solidarity Worldwide. Here is a link to their Take Action page: CSW Take Action. You can send letters of encouragement to those who have been imprisoned for their faith and you can also petition embassies and government officials on their behalf. It only takes a few minutes to make a difference. If you sign up for their e-newsletter you'll receive prayer reminders and action updates.