Send out a unique (unprotected) link per user I'm the admin of a Drupal site with 200+ users. I sort of rolled into this, so I'm no Drupal expert, although I've managed to understand it quite good now.

This is a site for our sportsclub and we want all existing users to confirm their membership (of the club) for the coming season.

We would prefer to do this a simple as possible and send each user a link which, when clicked on, will confirm their renewal. Ideally, this is a link with some sort of unique hash, so we can make it unprotected. This would avoid having to log in. 

We want to do this (keep it as simple as possible) because we've noticed a lot of members just don't do it (go to the site, log in, go to the correct page if not already there, and click the yes link to renew).

Is this possible (with a module perhaps)? Sending out a unique link per user?
I don't know of a single module to do this.  

I would suggest looking at the VBO module (views bulk operations).

You can create an "email" action and customize what gets sent.

From your description I think the biggest barrier you're facing is that users don't want to login,  and you'd like them to just click a link.

To do that you're going to have to roll your own module and likely make use of a menu hook with a callback to a function that processes the link.