Don't know if this is common knowledge so I thought I'd share. For building web/mobile application mockups there's a set of stencils available in svg format (amongst others) on the yahoo developer page http://developer.yahoo.com/ypatterns/about/stencils/
Please share if you know other svg stencil places.

Aah, interesting
I'm curious though, about the description:
"Yahoo! Design Stencil Kit version 1.0 is available for OmniGraffle, Visio (XML), Adobe Illustrator (PDF and SVG), and Adobe Photoshop (PNG), and covers the following topics:"
It doesn't mention Inkscape, so I wonder if you've actually used them with Inkscape? I know it says SVG, but that's not always a guarantee that Inkscape can handle it. Or maybe it's just directed at proprietary apps for some reason?

I have downloaded and used the template. It's pure svg, and inkscape has no probs with it.
I think they mention the applications as well as the file extension, to give people a clue, if the extension itself doesn't ring a bell. And from my experience at work, most people don't have any idea about which application supports which filetypes..or even have a basic working knowledge of graphics (or other) file types and their virtues and limitations. [edit] that includes some programmers as well.

Thanks.