There were three major changes (in addition to some minor changes) to the MLA format from the 6th edition to the 7th edition, which came out in 2009. I found the three most obvious changes all simplified the process and made the works cited page much cleaner. I was in favor of all three.
- Italics for titles rather than underlined, in text as well as in works cited list.
- Specification of the medium of publication in the works cited list, as in "Web," "Print," or "DVD." This comes at the end of the entry.
- No more URL's in works cited list, unless specifically requested by the instructor or if the source will be impossible to find without it. (This was a much needed change.)
A few other, much smaller (more detailed) changes, can be found in the 2nd link below.