I know that Rick Brannan has a little script on his blog that allows you to get the ISBN numbers out of your Libronix Bibliography. However, as he himself comments there, it doesn't limit itself to the books you own, but pulls up everything that your Libronix installation recognizes.
I was trying to get my Father-in-law's collection listed completely in LibraryThing, but of the 219 Libronix resources he owns, the scrip generated 835 resources! Anyone know of another way to get this information? Anyone know if this feature is being added to the bibliography export options for V.4?