I bought and oil on board painting at an estate sale and it has a signature of C. Westchiloff in the lower left corner. It has a stamp on the back that says Borin Art Product, Chicago 8, Ill. Is this worth anything?

If it is an original, yes, it is probably most definitely worth something. You should contact this gallery:

19th Century Paintings - Mark Murray Fine Paintings (http://www.markmurray.com/)

Here's one that recently sold on ebay:

193: CONSTANTIN ALEXANDROVITCH WESTCHILOFF - (eBay item 140144275406 end time Aug-28-07 09:32:53 PDT) (http://cgi.liveauctions.ebay.com/ws/eBayISAPI.dll?ViewItem&category=28247&item=140144275406)

Another one listed here for between $6-9,000:

ARTISTlisting - July 17-18, 2007 (http://www.jacksonsauction.com/July07_catalog/artistlisting/JUL07_alpz.htm)

I am wondering the same thing, I have the ocean one, I have found several online claiming to be original