Where can I find out how much short interest has been placed on a specific stock?

I do not believe it is possible because I do not believe that short interest is reported that frequently. I believe short interest is only reported twice a month and is several days old by the time it is reported.

If twice a month data is adequate for your purposes you can find it on the web. For example, here is a one year history for HOV.

http://www.nasdaq.com/aspxcontent/shortinterests.a...

The values reported in the above example are in number of shares, so you would have to convert them to percentages if you really need percentages.

The only place I know that reports percentages directly is

http://bigcharts.marketwatch.com/

but it is in the form a a chart instead of a table. To get the chart use the "advanced chart" facility and click on "indicators" on the left hand side of the page. Choose "% Short interest" as one of the indicators then click on "Draw Chart".

Enter a ticker symbol and click on flash quotes and you should be able to find it.

http://www.nasdaq.com/

go to the exchange site - nasdaq or nyse. other site that have this are the wsj and barrons