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.
pdflayer - Free, powerful HTML to PDF API supporting both URL and raw HTML conversion. Unlimited document size, lightning-fast and compatible PHP, Python, Ruby, etc.
RunPDF - RunPDF is a free HTML to PDF Online Converter service.
PDFShift - Convert any HTML documents to high-fidelity PDF using a single POST request
Document Cyborg - Easily save a web page as a document (PDF, WORD, EPUB, ODT, RTF or Text)
Tcpdf - TCPDF: Open Source PHP Class for generating PDF documents