This is a free flat design UI kit where you will find the HTML5 and CSS3 codes for free.
This UI kit allows you to work alongside the latest version of Bootstrap.
If it’s features that you want, this UI kit has plenty to offer.
BOOTFLAT is an open source Flat UI KIT based on Bootstrap 3.1.1 CSS framework.
This is a flat design UI kit that is available in both PSD and HTML forms to suit your needs.
This is another flat UI kit that you can use. Unlike other options though, this one is meant especially for administrators.
This is a very useful UI kit that was first designed to be used for email user’s interfaces. It has dashboard elements.
This is a web user interface that is available in PSD, HTML, CSS and jQuery formats.
This is a web user interface for designers and developers, which is based on the free version of the Futurico web UI.
10. Web UI CSS kit
A lightweight and modular front-end framework for developing fast and powerful web interfaces.
Original Source: http://efytimes.com/e1/fullnews.asp?edid=137969