I would like to learn more about how the Air Traffic Control system works - are there any resources available which describe the system that would be suitable for a beginner or student?
Another good reference would be the training materials for VATUSA. This is part of an online system called VATSIM where people both fly and provide ATC virtually.
Although some of it does not apply to real operations (and of course none of it should be actual operations), it still covers real procedures based on the actual rules.
The basic guides do a good job of providing an introduction to the basic concepts, but the more advanced stuff is less helpful.
Other regions have their own VATSIM organizations, if you prefer a region other than the US.
In addition to the materials available, participation is also great for learning. Through VATSIM you can get training on the materials and then get hands-on experience working with (virtual) traffic.
The first two places I would start would be the FAA's Air Traffic Control landing page, and Chapter 4 of the Aeronautical Information Manual which deals with air traffic control (and is generally the level of information student pilots are expected to be familiar with).
While these references are both for the US/FAA air traffic control system there are strong similarities among the systems in most countries (the ones with the greatest variation would be countries where the military handles air traffic control).
If you're looking for more advanced information pretty much all of the operational and training manuals the FAA uses are available to the public. These are likely of more interest to someone studying to become an air traffic controller - the information in them is substantially more technical and "job-oriented" than what's presented in the resources above.
The Air Traffic Basics course is the first information new FAA controllers are exposed to, and it is available to the public. This is a comprehensive introduction to background aviation knowledge from a controller's perspective.
Beyond that and getting into phraseology, there is FAA JO 7110.65. This document is THE standard for U.S. air traffic control procedures. Everything controllers say comes from that book.