compare

Compare lets you perform side-by-side comparison and merge of your directories, files, and their content.

It lets you see changes down to the character level and copy changes between two different versions of a file as needed.
This lightweight application features clean interface with easy to understand controls and icons, no bloat (such as image or sound wave comparison, built in emacs editor, etc) and does not require you to create and manage projects. Just select or drag-and-drop in two items onto it and you're ready to compare and merge. It also remembers all recent items for each side so you can perform repeated comparisons easily.
(While there are no plans to jam in a bunch of features into this tool, a few exciting changes are coming, please see the website. And thanks for checking out this comparison and merge tool!)