Out of stock items

What is the best way to handle out of stock items on a website? Obviously trying to not have any items out of stock is best, but i have several vendors with long lead times so I will always have some items. In the past I removed out of stock items from the site. Now I have a new site and am debating the best option. I'm leaning toward keeping all items up on the site but using an app that will let customers be emailed when back in stock.