The reason that I was learning how to solder was to permanently connect three wires together in an RJ45-DB9 connector. The reason I was connecting the wires was to build a 5-in-1 cable, one of the projects featured in the book Make: The Best Of 75 Projects from the Pages of Make.
This is a marvelous book, full of interesting projects. Its contents are categorized into tools, electronics, microcontrollers, and so on. The cable is from the electronics section.
I chose the cable for two reasons. One was that among the 75 projects, this one actually seemed the most useful. The second reason was that it was a small project of relatively low complexity.
Even with needing to learn how to solder, this project is simple. More importantly, it was fun. The author of the project instructions, Mike Ossmann, suggests more adapters, such as DB-25 and Din 8. His web write-up gives nearly identical instructions as the book does, with added instructions for different connectors. I will report on my progress as things develop.