The Nottingham Hackerspace offered me some sugru so I could not resist to finally get around to fixing my power connector on my laptop. I know this is a common issue, but I thought I would go through and give a few tips I found useful.
Firstly, you really need to spend the time to make the power connector robust and reliable. Many of the connectors available from farnell/RS will either be rather expensive or won't have the right power rating. The other problem I found was getting one which was not by far too long. I ended up going to a maplin store so that I could actually see them and hold them up to my computer.
Once you have made up the connector, solder the wire as you would expect (red to the middle pin and black to the outer rim of the barrel) I found putting a bit of sugru at the end of the wires and into the end of the barrel jack quite helpful (clearly not at the metal end). This helps to prevent the barrel for being able to rotate free once the sugru has set, and will cause less strain on your wires.