Merge is the visual file comparison (diff), merging and folder synchronization application from Araxis. Use it to compare and merge source code, web pages, XML and other text files with native application performance. Directly open and compare the text from Microsoft Office (Word and Excel), OpenDocument, PDF and RTF files. Compare images and binary files. Synchronize folders. Perform code reviews and audits. Work with folder hierarchies containing thousands of files.

http://www.araxis.com/merge_mac/