I recently had a situation where the design of a website needed the combination of both mooTools and jQuery, two libraries acting on the same page. mooTools gave me a coverflow style effect, while jQuery handled the overlapping navigation tabsYou are probably asking why I didn’t convert one script to the other library. The answer is because of financial constraints. If I had the time I would wade through all the docs and, probably convert the lesser of the two (jQuery – simple html replacement, adding classes) to the other (mooTools mooFlow. I haven’t found a jQuery alternative yet).