tech-ranting.blogspot.com has an ediff tutorial. ediff is something I use extensively as it is so nice. It integrates with your source control system so you can ask it what changes you have made since last check-in (
One thing that isn’t well highlighted (so to speak) is how well ediff drills down on the exact change. It doesn’t just say “this line is different to this line”, it focuses on the exact change within the line. You can easily see here the tags that have been added to an old revision of one of my earlier posts.
The merging facility is also great. It has saved me on a number of occasions when clear^H^H^H^H^Ha well known source control system has dismally failed to merge branches.
What did I like about this tutorial? I learned something new (and Vedang, the tutorial author, had only looked at it for a day – I guess familiarity does breed contempt). So far I haven’t used ediff-directories as I didn’t know what it did. I imagined it would be similar to a recursive diff from the shell but it sounds like it does a lot more.