What are the practical use of LC oscillations? I understand how energy is transferred between the capacitor and the inductor in an LC circuit, but I am not sure what are the practical applications. Could someone please help?
 A: 
but I am not sure what are the practical application of it

A somewhat significant practical application is radio, from the simple:

to the complex:

A: If you add a resistance you get an RLC filter. One of the most basic AC filter.

A: As you likely know, the oscillations in a practical $L\,C$ network quickly die down, so, yes, I can understand the question of how an $L\,C$ tank circuit is turned into a practical, sustained output oscillator is intriguing.
Have you ever noticed how if you set up a microphone near speakers outputting the amplified former's output and speak into the microphone, the "feedback" doesn't manifest itself as an echo of your voice getting louder and louder. The feedback is often a pure tone: all the Fourier components of the noise into the microphone are amplified at first, but the most gain is imparted to those which come back, after the loop delay, to the microphone in-phase with original signal. So these get more gain than the others (which tend to quench themselves though destructive interference) and if, say, the loop gain for two similar amplitude Fourier components is $A_1$ and $A_2$, then after $N$ loop recirculations the ratio of the component amplitudes is $(A_1 / A_2)^N$. The system thus swiftly selects a narrow range of frequencies. The full story of how the loop's phase helps selection through constructive interference is quite complicated, because it depends on the nonlinear dynamics of the amplification supplying the energy to the system, but this idea of letting the maximum gain Fourier components dominate others exponentially with circulation number is the basic idea.
The $L\,C$ oscillator is a variant on this: the voltage across parallel $L\,C$ network selects Fourier components of an amplifier's output current, which is, in turn, driven by feeding this voltage back into the same amplifier's input. After a few recirculations, only frequencies very near the $L\,C$ circuits peak in the current to voltage transfer function are significantly present, even if the $L\,C$ is quite lossy and the transfer function peak thus rather broad.
A: Security tags on products in retail stores.   This recent article http://edn.com/electronics-blogs/living-analog/4421923/Thixotropy describes how they work.  The tag is foil and plastic, made into an inductor and capacitor.  It resonates at 8.2MHz, sensed by gadgetry surrounding the store exits.  A strong pulse of power applied by the cashier damages the LC circuit so the customer can take the item home.

