[R-SIG-Finance] getSymbols in quantmod

[babel at centrum.sk]

Dear friends
I would like to ask you, if there is an easy way,how to determined the correct symbol and the correct way to write it. Some symbols work fine and one can easily make up what the symbols are for example
getSymbols("GOOG",src="yahoo")
getSymbols("AAPL",src="yahoo") 

but how to find the other symbols for example currency pairs or commodities? Doesnt mean if they are from Yahoo or Google or FRED. Should I look in URL address in yahoo or google finance? And for which symbols I must specifie the start date, and other attributes? Some cheat sheet will surely help other people too. Many thanks you are doing a great job. 

Sincerely Jan