Several students have had to select an open source license for their creations recently -- including Fima and Cesar -- and this has provoked some interesting comments and discussion. Cesar's recent blog post reflected a common sentiment:
I canít really see anyone commercializing this or putting into some sort of binary extension, so I donít think the GPL would really benefit me.
But I think that part of the question should be: Which license will lead to the widest possible use of my work? Conditional cooperation theory, the overall vitality and productivity of the community, gains in personal reputation -- all of these support choosing a license that will make it easy to reuse what you've done, which means a license that is compatible with the widest range of projects that may be interested in your code.
The most popular Open Source license is GPL2, so using the GPL2 ensures compatibility with a huge codebase. Unfortunately, its successor, GPL3, isn't nearly as widely used, and was rejected outright (at least initially) by some projects. The LGPL and BSD License are permissive licenses that encourage reuse. Specific open source projects will have their ownlicenses.
Perhaps the best option, then, is to select the licenses that are used by the communities closest to your project, and consider dual- or triple-licensing (this works for content as well as code). You'll be in good company -- after all, some very successful projects use a tri-license.