When I work on a project in RubyMotion I often come up with small extensions of classes that I would like to share between projects. Usually these extensions are small, and not really worked out into detail. For example: a small extension on the time class. What is a good way to share these small extensions between projects?
Probably the best way to do this is to create gems. It is a good practice to find things to extract from your code into gems anyway, because it alleviates the testing that is expected for that project, as the gems should themselves be well tested.
I have to mention Ruby Facets as well, it is a successful project where people contribute to those things that may be more generally helpful. And you can simply include the facets that you need as you need them for each project.