A Saturn return is the transit event where Saturn comes back to the same place where it was located when you were born (aka where it is in your natal chart.) This happens approximately every 30 years and is often characterized by major changes in one's life. The exact changes can vary a lot based on what's going on with your natal Saturn (what sign and house it's in, its condition, the condition of its ruler, aspects to it, etc., etc.) and what other transits you have at that time.

Since it's something we all go through it's definitely a big topic that gets sked about a lot here, and understandably people want to hear about others' experiences with their returns, especially when other factors like the house Saturn lives in are the same. There's a great website called http://www.SaturnReturnStories.com where you can go check out lots of information on returns, see stories of Saturn returns, and submit your own stories to share. I highly recommend it.

For those of you who prefer reddit discussions, please share your Saturn return stories here in this thread and we'll sticky it so people can find it for a while to come! Be sure to include the house and sign and any other info about your Saturn that you might think is relevant.