IF I accidentally unplug a memory card when the card reader with it in it is in the computer what will happen?
if it damages the memory card, how do I Recover the data?
99.999% of the time absolutely nothing happens. Flash memory can only be corrupted if data was being written at the time, and when it does get corrupted usually only a single page will corrupt.
You still haven't said if you have seen corruption or just wondering what to do when it happens. The two are very different. If there is corruption, you might be able to recover data using Rescue Pro or similar recovery software. If you want to protect yourself from corruptions, just back up the data!