I just listed a book this afternoon and now it is showing up on my main page under a tab that says "Wishlist Hold'.  Does that mean it was a wishlisted book and someone has requested it?

It does mean that it's a wishlisted book, but the member has yet to accept the offer and officially request it.  When a wishlisted book is posted the member who's first in line for the book has 48 hours to accept or decline the book.  At the end of the 48 hour Wishlist Hold period, the offer will time out and move on to the next member in line.  This continues until either the book is accepted or the line runs out, at which point the book will be posted into the system.

Thank you for clearing that up for me.