If you had subscribed for SW:TOR previously but left for whatever reason, you can play for free from April 13th to 19th to check out the new and improved SW:TOR 1.2.

You don't need to do anything, just log in, download the update, and play.

Hope to see you guys (I'm looking at you Lung, Monlee, Banana, etc.)

Details:
http://www.swtor.com/legacypromotion