Kurt Cobb has given a rather neat picture of a party that is about to be pooped . He begins with discussion of balloons filled with helium which are a red-herring to the underlying connection of helium to natural gas, and that if helium is about to run short (so no more party-balloons), so is the world's provision of natural gas. Helium is a remarkable material, with some unique properties, especially in liquid form, as it is used as a coolant, for example to run superconducting magnets, e.g in MRI (magnetic resonance imaging; the safer alternative to x-ray body scanners) applications. It is also used as a blanket-gas to shield sensitive materials from atmospheric oxygen, and enable certain chemical reactions to be performed and indeed specialist welding operations in which the weld is stronger when the metal surface has not been exposed to reactive atmospheric gases. Helium finds further application in gas-cooled nuclear reactors, as a heat-transfer agent.
Most of the world's helium is found in the United States, and it is recovered by separating it from natural gas with which it is coincident. Helium arises from the decay of radioactive elements like thorium and uranium, whose atomic nuclei decay to form alpha-particles - helium nuclei - which form elemental helium by capturing a couple of electrons from their surrounding media. The majority of helium - since it is a material of low mass - simply rises into the atmosphere and escapes the Earth's gravitational pull to dissipate into outer-space, but some of it becomes trapped in the rocky formations of gas-wells, from which it may be recovered in concentrations of up to 7%.
As is the case for all fossil-materials, natural gas was laid-down in long times past and we will eventually use it up, especially against current rising demand for it. It is the same story for oil, ultimately coal, and indeed uranium, so most of our current energy production methods are living on borrowed time. Helium is also a fossil material, but it can be recycled, as I recall from working at the Paul Scherrer Institute (PSI) in Switzerland, which uses huge amounts of liquid helium to cool the vast array of magnets used to steer beams of charged particles, particularly muons, toward particular experimental arrangements.
At PSI, the helium is recovered and liquefied on site so it can be recycled, since is a comparatively pricey substance, and another recollection about it is that it diffuses through the steel walls of cylinders in which it is stored under high pressure. If you get a new helium cylinder and don't use it for say, 6 months, when you attach the pressure valve, about half of it has gone!
While the world would certainly not grind to a complete halt if all its particle physics institutes had to close-down in the absence of helium, modern medicine would be disadvantaged and need to return to using x-rays as a means to "photograph" the inside of human bodies as in the CT-scanner alternatives to MRI. If we run short of natural gas, however, the world won't run on with this fact largely unnoticed, and peak gas looks to hit at around 2025 ... a mere 15 years time, and more and more of it is used each year, along with all other sources to slake a dust-dry thirst for energy.
I have written before "Metals Shortages"  about how indium and gallium are likely to run out in 5 - 10 years with impacts on any and everything electronic, at least in the complex matrix of electrical devices. Hafnium is another metal whose days are numbered, which is an essential component of computer-chips and also employed as a thermal-neutron absorber in nuclear control-rods, and may literally run-out within 10 years. Peak oil we all know about, but peak gas, peak uranium and peak coal will follow. There is in fact a peak in the production of all materials that were laid down in the distant past, and we are using them up at an expanding rate.
Even if we manage to solve our energy problems, we won't have enough "stuff" to make things from.
 "Let's party 'til the helium's gone", By Kurt Cobb. http://resourceinsights.blogspot.com/2009/05/lets-party-til-heliums-gone.html
 "Natural Gas: how big is the problem?", By Louis de Sousa. http://www.theoildrum.com/story/2006/11/27/61031/618
 "Metals Shortages", by Chris Rhodes: Chemistry and Industry, 25th August 2008, p21; the article is also on http://www.scitizen.com/stories/Future-Energies/2008/09/METALS-SHORTAGES-/ and on this blog too: http://ergobalance.blogspot.com/2008/08/metals-shortages.html