The new Access Control Levels (ACL) are a huge part of Joomla 1.7. In previous versions you had limited control over that user could and could not do. Now in the 1.6 / 1.7 / 1.8 version of Joomla you have very detailed control.
However, the system is now substantially different. Here is a detailed guide to the best ACL tutorials around.
We also recommend four steps to get you quickly stared and up-to-speed. Let's see Step 1 ...
Introduce Yourself to the New ACL
Step 1: Start with this tutorial from Joomlashine. They take you through a comparison of Joomla 1.5 and 1.7 and explain where and what the new ACL settings are.
Learn by Doing. Try Some ACL Examples
Step 2: Try this specific example from Yireo who walk you through setting up a "Marketing" user who can add and edit their own content.
Step 3: Download this free chapter from my new Joomla Explained book and try the three examples.
Step 4: Jen Kramer posted a two part tutorial on Joomla.org. In Part 1 she explains front-end viewing and controlling what your users can SEE. In Part 2 she focuses front-end editing and controlling what your users can DO.
An Extra Extension to Help Learn ACL
Because the ACL settings are spread throughout the Joomla interface, the ACL Manager extension can be a big help. Read more about ACL Manager here.
More Advanced Tutorials
For those who want to dig deeper, there is also this fairly geeky tutorial on the Joomla docs site.
Joomla ACL Videos
If you learn better via videos, there are also these videos to help you out:
Joomla ACL Presentations
Here are two presentations from recent Joomla days that also help explain ACL: