We do quite a bit of software development at AADL, and some of the work we've done may be of interest or use to other libraries. Our website is powered by the completely awesome open-source CMS Drupal, and much of our development takes the form of drupal modules. We also run Innovative Millennium (Triple-I), so many of our drupal modules use shared code libraries or PHP classes that we've developed to interface with our III server. Here are several tools you may be interested in, especially if you've got PHP experience or are running III.
III-PatronAPI: This is a PHP script that interfaces with III's optional web-based PatronAPI module and makes that data more easily available to PHP projects.
SOPAC & Middleware source code: SOPAC is what we call our social features on our public catalog. It includes the ability to add ratings, reviews, and tags to items in the catalog and integrates with our drupal patron account module.