Visual Editor

• bootply.com – online visual bootstrap editor
• pingendo – free, native (download and install)
• pinegrow.com – paid (starts at usd49), native + online demo
• layoutit – free, online editor
• jetstrap.com – paid

Snippets, tools, themes etc.

• bootsnipp.com – snippets, form builder
• startbootstrap.com – theme and templates

Others

• bootstrap magic – change theme, color and other default look for bootstrap based on your preference
• codiqa.com – build mobile app easily. nice and easy interface
• x-editable – library to easily update data in-line without whole form submission
• bootbundle.com – theme, template, plugins etc. many sites on one.
• list of more plugins and tools