Twitter Bootstrap is a great front-end framework that lets you quickly prototype new web projects. Here is a list of great resources that gives even more power to the Bootstrap framework.

Metrostrap – Bootstrap skin

Metrostrap is a bootstrap minimalist (metro-like) skin that gives you a solid base to start your projects.

Fuel UX

Fuel UX extends Twitter Bootstrap with additional lightweight JavaScript controls. Other benefits include easy installation into web projects, integrated scripts for customizing Bootstrap and Fuel UX, simple updates, and solid optimization for deployment. All functionality is covered by live documentation and unit tests.

X-editable

This library allows you to create editable elements on your page. It can be used with any engine (bootstrap, jquery-ui, jquery only) and includes both popup and inline modes. It’s new life of bootstrap-editable plugin that was strongly refactored and improved.
Please try out demo to see how it works.

Bootstrap-Modal

Extends Bootstrap’s native modals to provide additional functionality. Introduces a ModalManager class that operates behind the scenes to handle multiple modals by listening on their events.

Bootswatch

Bootswatch is a collection of free themes for Twitter Bootstrap.

Free Twitter Bootstrap UI Mockup Templates for Keynote, PowerPoint and OpenOffice

Prototype Bootstrap-based apps using your favorite presentation tool. The following vector UI components have been designed from scratch in Apple Keynote, Microsoft PowerPoint and OpenOffice Impress, and are fully editable and customizable without needing any additional design tools.

A date range picker for Twitter Bootstrap

This date range picker component for Twitter Bootstrap creates a dropdown menu from which a user can select a range of dates. It was created for the reporting UI at Improvely.

Font Awesome

The iconic font designed for use with Twitter Bootstrap.

Twitter Bootstrap Button Generator

The easiest way how to set up your buttons based on Twitter Bootstrap in a seconds.

Grid displayer for Twitter Bootstrap and Foundation

In-browser web design made easier with this bookmarklet which displays the grid of your favourite front-end framework.

bootstrap-wysihtml5

Bootstrap-wysihtml5 is a javascript plugin that makes it easy to create simple, beautiful wysiwyg editors with the help of wysihtml5 and Twitter Bootstrap.

Jetstrap

Jetstrap is a 100% web-based interface building tool for Twitter Bootstrap.

Beautiful Buttons for Twitter Bootstrappers

This is an extension to the Twitter Bootstrap framework. It makes creating pretty buttons easy.

jQuery UI Bootstrap

This is a great Goodie item for you in reference to Bootstrap. jQuery UI is a great library of interface elements and it includes all the widgets you can ask for.

divshot

Bootstrap-based mockup interface builder for Web apps.