Also: you have to remember to keep checking things in to your source control repository. It's good discipline, all of it -- it keeps you on your toes when you switch to another machine and it doesn't have the nifty shell script you just wrote, and so you have to switch to the machine where you carelessly orphaned it, and check it in to your source control repository (logging a comment explaining just what the heck it's for, because I promise you you'll have no idea later), switch over and check the file out again to the other workstation.
This also has the side effect of making your overall environment more consistent and modular, because you're less likely to create something that has a dependency on some artifact of the workstation you happen to use the most.
$ svn update coffee
svn: Failed to add 'coffee': that's in the real world, you have to go get it yourself