Many thanks to Brenda who pointed out that all four volumes Donald Whyte's A Dictionary of Scottish Emigrants to Canada Before Confederation are available on CD-ROM. Read more about it here.
While searching for the CD Brenda mentioned, I found a portion of A Dictionary of Scottish Emigrants to the U.S.A. on Google books. This version can also be purchased as an eBook.
Find a copy of one of Whyte's Emigrant Dictionaries at a library near you via WorldCat here, simply click on the hyperlinked title of the volume you are interested in.