Well, officially of course the LSAT tests are not for free. The LSAC sells these tests in there "10 Actual Official" Series. The LSAT company that I work for has to pay over $200 per student in order to use official questions in the company's books.
The most obvious place to get additional GMAT questions is in the Official Guide Verbal Review 2nd Edition. This has about 80 critical reasoning questions.
You can get Critical Reasoning GMAT questions by purchasing materials from various companies that are represented on this site: Veritas, Princeton, Kaplan, Manhattan. And as mentioned above there are also some newer companies out there that are entirely online. I have not seen many of their critical reasoning questions so I cannot say.