SourceForge - The Complete Open-Source and Business Software Platform.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
openDesktop.org - The website openDesktop.
DocRaptor - As the only API powered by the Prince HTML-to-PDF engine, DocRaptor provides the best support for complex PDFs with powerful support for headers, page breaks, page numbers, flexbox, watermarks, accessible PDFs, and much more
OSOR - OSOR is the Open Source Observatory, a project to provide a framework for developing and executing autonomous observations.
PDFCrowd - Pdfcrowd is a Web/HTML to PDF online service. Convert HTML to PDF online in the browser or in your PHP, Python, Ruby, .NET, Java apps via the REST API.