I just found a new reason to regret the fact that there aren't any legal Calvin and Hobbes ebooks. It's a new search engine built just for this one comic strip by someone who loves it as much as I do. Right now you can search by date or by a specific word or phrase that was used in the strip.
The image links are broken at the moment, and I should warn you that they are also pirated. There is no legal digital copy of this comic strip.
P.S. I regret the lack of ebooks because this could be built into most any ebook app. It would probably need to be a standalone app, though. But I'd buy a copy.