ECMerge Standard (Solaris) Description:

ECMerge is a powerful utility for merging text files and synchronizing folders visually.
ECMerge provides syntax colouring for C/C++, Java, XML, HTML, ASP, PHP, Visual Basic, SQL and many others languages. Unicode and 100 national encodings supported.
In-line differences at word or character level, automatic formatting for XML-based files at loading.
Save your work at intermediate situation and restart it later! Prepare recurrent comparisons with Templates.
Edit files and edit individual lines after comparison.
Generate Unix patches between files.
Many customizable options :
Text file comparisons : ignore whitespaces, case, line ending characters, lines matching patterns (with regular expressions),...
Folders comparisons : ignore identical files, ignore files absent in a given hierarchy, ignore files matching name...
Customizable display, colours and localization.
Bookmarks in both files and folders comparisons.
A shell extension is provided: select files or folders one by one, or 2 or 3 at a time to compare them visually with ECMerge.
Supports command line options.
Can be used as a replacement of many SCC own merge tool, for better display of changes and more efficient merges.

Also exist:
A Linux and a Windows version of ECMerge
A bundle of ECMerge for all platforms (Windows, Linux and Solaris)
ECMerge Pro (compares and merges 2 or 3 files & folders)