Brett Bonfield has a great post, actually more of a long essay or article, on open source library software projects.  W-E-B-S-I-T-E, Find Out What It Means To Me (great title, but certainly more limited than the post’s topic) covers a wide range of software, the reasons people use (or don’t use) them, and the status of several of the larger projects that currently exist.

There is a lot of information in the post, and links for further exploration.  This just made my recommended reading list.