PDF Joiner - This online tool allows you to join several PDF documents into a single file, free of charge.
DocuPUB - DocuPUB is an online file converter, file merger, file compressor, and file resizing tool.
PDFTK Builder - PDFTK Builder is a free graphical interface to for PDFTK, making it much easier to use.
PDFChef Merge PDF - PDFChef Merge PDF is an online tool that allows you to merge multiple PDf files into one quickly and securely.
7-PDF Split & Merge - Functions: Split pdf-files, Merge pdf-files together
CleverPDF - 27 Powerful and Free Online PDF Tools