ECMerge Pro (Windows) 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 Solaris version of ECMerge
A bundle of ECMerge for all platforms (Windows, Linux and Solaris)
Key features

Ellie Computing Merge is the comparison and merging utility for heterogeneous environment teams.

Fast: Ellie Computing Merge compares the documents in parallel when they are launched from folders views and profits from Hyper-Threaded as well as Double-Core processors.

Easy to use: Ellie Computing Merge highlights differences in side-by-side views and text blocks that are conflicting. Full undo/redo is provided. You can save your work at intermediate situations for text files as well as for folders.

Source code review: Compare source code to older versions and identify what has changed. Java, C#, C++, Visual Basic, Perl, PHP, Delphi, etc. Syntax colouring helps you to merge by avoiding typo errors.

Merge: Merge your changes and those of your co-workers based on a common ancestor into one copy. One-click to merge a block of text. Editable output. Unlimited undo/redo.

Folder comparison: Analyze differences between 2 or 3 folders hierarchies or ZIP/RAR archives and synchronize them.

Integrate it in your development environment: Call Ellie Computing Merge from your SCC solution to perform comparisons and merges. Configure periodical batches to generate reports that will help you in evaluating the next branch integration task. Launch a comparison on any file or folder from your file system with the Windows Explorer Shell Extension (Windows only).