Google Finance offers a simple way to do this, using the GOOGLE_FINANCE function.

There are simple tutorials for doing this for stocks.

You need to form the symbol attribute by combining the exchange symbol(NYSE, NASDAQ, etc) and ticker symbol (AMZN, GOOG, etc.).

For example, So NASDAQ:AMZN. The complete code to use to retrieve the prices is

=GOOGLEFINANCE("NASDAQ:AMZN")

If you don’t know the exchange symbol, just search for the stock on Google Finance. The search bar will show the code to use as [exchange]:[symbol].

Note: Ensure that there you don't include any spaces in the symbol. NASDAQ:AMZN should a single literal.

This also works for tracking mutual funds. For example, searching for on Google Finance UTI Nifty 50 Index Fund will return:

So you would use the code as:

=GOOGLEFINANCE("MUTF_IN:UTI_NIFT_50_FGX2CX")