You can get the source and open issues on Github.
sphinx-better-theme is compatible with Sphinx 0.6.4+ and Jinja 2.3.1+. Older versions may work but have not been tested.
v0.1: Basic CSS-customizable style that looks nice in its default state
v0.11: Add easy Google Analytics support
v0.12: Improve base styles, responsive layout, document usage with Read the Docs
v0.13: Further style improvements, relbar shows only full titles of next/previous links
v0.1.4: Semantic versioning, mobile bug fixes, sidebar slimming, style improvements
v0.1.5: Remove a few useless options, allow remote CSS files, fix Google Analytics integration
v0.2: (planned) Rewrite markup to be semantic and customizable
v1.0: (planned) Extreme documentation polish and rounding out of edge cases
kr-sphinx-themes has two nice, clean themes used for many popular (and good-looking) projects.
sphinx-readable-theme is a theme optimized for readability of apidoc-generated docs.
sphinxtheme-readability is another attempt at a clean theme.
Cloud is a feature-rich theme with a responsive layout.
A few different themes are available for download at sphinx-themes.
Read the Docs uses a custom theme as the default for all docs hosted there.
The Julia language also uses an interesting custom theme.