jQuery Calx is powerful yet easy to use jQuery plugin for building calculation forms or calculation tables. It parses provided formulae and performs calculations, scans for form changes and updates results automatically, and formats plain numbers into currency format, ordinal numbers, etc. It is suitable for both simple ($A+$B) formulae and complex ones such as ($I*$P*((1 + $I)^$N)) / (1 - ((1 + $I)^$N)).
MockMockWeb is a Heroku-ready Node.js-based Web application server which allows you to mock up a website in seconds. It allows you to instantly launch a website which sends an empty page (with status 200) to any request/URL and edit any page on the spot. You can also edit the layout shared throughout your website. It lets you build a mock (sometimes real) website in a request-driven interaction.
file2password is a utility that allows you to select a file (picture, document, music, etc.) and generate a secure password based on it. This means that there is no need to remember any password - just a picture or a filename. It is small (2 KB plus CSS), highly secure as it does not upload or shows the file used, supports drag and drop, can use online storage, and requires no server-side scripting.
jquery-simple-slideshow is a simple, low-config, jQuery-based slideshow. It does not require a complex pre-defined HTML structure. One image is added to the HTML, and clones will be created at exactly the place of the original image, and the additional images will be displayed according to the desired config.