The 26th of May 2007 (this week's) issue of New Scientist has a cover article / special investigation titled "
World Stripped Bare: the state of the world's mineral resources
". If you get this message in time, buy the magazine... 
They claim that if we keep on consuming at today's rate, we will exhaust our supplies of ....... in x number years. I may as well just type out the whole thing here, hope I'm not breaching any copyright.
name - years left if the world consumes at today's rate - what it's used forAntimony        30 years - drugs 
Aluminium   1027 years - transport, electrical, consumer durables
Copper            61 years - wire, coins, plumbing
Gold                45 years - jewellery, dental
Indium             13 years - LCD screens
Lead                42 years - lead pipes, batteries
Nickel              90 years - batteries, turbine blades
Phosphorous  345 years - fertiliser, animal feed
Platinum         360 years - jewellery, catalysts, fuel cells for cars
Silver               29 years - jewelry, catalytic converters
Tantalum        116 years - cellphones, camera lenses
Tin                   40 years - cans, solder
Uranium           59 years - weapons, power stations
Zinc                 46 years - galvanising
Figures not available for Rhodium, Hafnium, Germanium and Gallium.
"The calculations are crude - they don't take into account any increase in demand due to new technologies, and also assume that current production equals consumption. "   
That's why this data is scary. Because we expect consumption to *increase* as more people access more technology. 
Example 1: 
Reserves of Tantalum (used for cellphones) are estimated to last 116 years at current rates of consumption but could run out in as little as 20 years if everyone on earth consumed at just half the American average. 
Example 2:
Reserves of Indium (used for LCDs) are estimated to last 13 years at current rates of consumption but could run out in as little as 
4 years if everyone on earth consumed at just half the 2006 US per capita rate. 
The point is that these resources are finite. "Unlike with oil or diamonds, there is no synthetic alternative .... once we have used it all there is no way on earth of getting any more".
Other data in the article includes "Proportion of consumables met by recycled materials (%)", and World Totals (where the minerals are - Australia has the most Uranium and Aluminium, and more than half the world's Hafnium and Tantalum).
All in all this is an excellent article in a fascinating magazine, so go buy it!