Learning how to build circuits is a lot of fun and can be very useful for projects around the house or to establish a lucrative career in electrical or electronics engineering. There are many resources available online that are free and help you get started easily. One popular circuit to learn is a circuits videos and schematics because of its versatility in a variety of applications. It implements some very basic but powerful electrical components that, when combined, produces a circuit akin to those used in millions of different types of electronics.
The reason you want to start learning 555 signal generator operation as soon as possible is because you will learn the majority of the fundamentals of circuit analysis and design all in one circuit, but also because of the incredible utility this specific type of circuit has to offer for many types of implementations. The most famous of the basic 555 timing circuits is the one that allows the blinking of an LED (light emitting diode) at the rate which you specify when you build the circuit. The rate of flashing/blinking is decided by the time constant of your circuit, which is calculated by your resistance times your capacitance.
The best way to get started with building tutorials on learning circuits analysis is to look up tutorials online, but also look at the datasheet of the IC. A datasheet usually comes in PDF format available for a free download and has all of the characteristics of that product specified by the manufacturer. Nearly all electrical and electronic components have a datasheet for each specific model or one for similar models in a certain series of closely related products.[youtube:APbnnbjuWas;Flashing Light Emitting Diode circuit and resistance capacitance TC;http://www.youtube.com/watch?v=APbnnbjuWas&feature=related]
Digital devices incorporate 555 timing circuits to provide a serial clock function that times the sequence of bits that comprises the binary code that makes them work the way they were intended. This means that 555 timing circuits are useful for much more than just timing or counting. Hundreds of thousands, or even millions, of electronics used today incorporate Schmitt Inverter and would not function without them. Now do you see the importance of why you should learn them right away?
Really to get into electronics design, electrical engineering, or robotics, learning 555/556 timing circuits is a must. You cannot avoid circuits tutorials and projects so you may as well do yourself a favor and begin to understand them early on. Because they are used in very complex electronics does not mean you cannot use them for extremely simple and rudimentary projects.
For a good tutorial on timer projects using LM555, check out http://www.555timercircuits.org. Check out oscillators to find all the details.