Meld is a visual diff and merge tool. It integrates with most version control systems. The diff viewer lets you edit files in place (diffs update dynamically), and a middle column shows detailed changes and allows merges. The margins show location of changes for easy browsing, and it also features a tabbed interface that allows you to open many diffs at once.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.