Sputnik is a wiki written in Lua and running on top of Kepler. It is also a platform for building a range of wiki-like applications, drawing on Lua's strengths as an extension language. Out of the box Sputnik behaves like a wiki with all the standard wiki features: editable pages, mild protection against spam bots (you need an account to edit pages, but anyone can create an account with no questions asked), history view of pages, diff, preview, per-page-RSS feed for site changes. At the same time, Sputnik is designed to be used as a platform for a wide range of "social software" applications. A simple change of templates and perhaps a few spoons of Lua code can turn it into a photo album, a blog, a calendar, a mailing list viewer, or almost anything else. Demos are available on the site.