I noticed that a book that I requested was supposed to have been mailed by yesterday but it hasn't been marked mailed.  I know that there is a two day "grace period" but what happens after that?  If the book is never marked mailed, will I get my credit back?

I can never remember how all that goes...but I do know that just because it wasn't marked mail, doesn't mean it wasn't mailed.  Sometimes they forget to mark it mailed, or wanted to wait until after it was mailed and then didn't get back on line.  But, yes in the end you will get your credit back.

Well I have 2 to send that had mail by date of today. I have the wrapped up and ready to go but I never made it to the PO on Fri and our PO is closed on Sat.  So they are going in the mail a day late.  It's possible that this person just didn't make to the PO in time on Sat and is going to mail them on Monday.

If they printed the label, I would send a PM though just incase they forgot to mark it mailed. Then you can stop the reorder if they say they've sent the book. The system will reorder the book for you if it's available in the system adn you could end up with 2 copies.  If they didn't print the label then maybe they aren't going to mail it afterall. It happens-could be a new member who has decided they don't like doing PBS afterall. 

From the Help Center:

What if the sender agrees to send the book, but doesn't mark it mailed before the deadline?

• If there is another copy of the book available, your request will automaticlally be passed along to a new sender. 
  • You will not get an email notifying you if this happens.
• If there is not another copy of the book available, the request will be canceled, you will get your credit back, and the book will go onto your Wish List. 
  • You will get an email notifying you if this happens.

Since it is possible that they sent it, but forgot to mark it mailed, you may want to send them are reminder e-mail before a request is sent to a new sender just in case so you don't end up with two copies. You don't have to give a credit to someone who doesn't mark it mailed and you get a second copy from the system, but I find it less stressful and more guilt-free to try to find out before hand if the 1st person actually mailed the book.

Thanks for the info.  I hate to seem pushy by sending a PM but I also don't want to end up with two copies of the same book!  I guess I'll send a PM.