I should read this, maybe you want too.
Choose a pattern and print it. Nice tool by countryman Rastislav Blaha.
Very nice stencil by good people at Viget.
You get all the Bootstrap UI element but even better, you get all the great Glyphicons not as PNGs but as Omnigraffle shapes allowing you to resize them without losing quality and to color them or doing anything else you could do with a shape.
All in all, this is my new favourite wireframing stencil.
Quick tip: To install, just drag the stencil file to the OmniGraffle icon at the Dock. Then just press Cmd + 0 to show the Stencils panel.
Jetstrap may be useful.
Via @jakubspanihel
Moqups is a nifty HTML5 App used to create wireframes, mockups or UI concepts, prototypes depending on how you like to call them.