Here are some nice examples created with ForeUI, including low fidelity sketch, medium fidelity wireframe and high fidelity prototype. They are not just clickable mockups, they are real interactive prototype with all kinds of interactions. Some of them could even work as functional web applications, as they have web services on their back.
Please click any thumbnail to load the corresponding HTML5 simulation in your web browser.
You may also be interested in downloading the plot files in ForeUI Store.