The Wisconsin state library agency publishes Public Library Space Needs: A Planning Outline / 2009. This publication, by LPA's founding principal, links a library's service goals to its space needs and offers a means to make an initial estimate of the library space needs.
The Whole Building Design Guide website, maintained by National Institute of Building Studies has a page devoted to libraries.
The "Libraries" tab at Library Journal's "Designing the Future" website is a great jumping off point for stories about important new libraries, including the latest group of LJ's New Library Landmarks. Check out earlier groups of landmark libraries, too.
Every year, American Libraries highlights its Design Showcase, always an engaging summary of newly-opened buildings.
Along with LJ's yearly round-up of featured designs.
The Designing Libraries website offers an alternate and illuminating perspective on library design that is not Ameri-centric.
Likewise, the Library Buildings and Equipment Section of the International Federation of Library Associations explores topics relating to building design from a global perspective.
Architectural Record highlights new library projects on its Building Types Studies "Libraries" page and you can link to more examples from there.
Since 1963, the American Institute of Architects and the American Library Association have honored excellence in library design through their jointly-issued Library Building Award. Recent honorees are highlighted on both the AIA and ALA websites. Link to the AIA site here and click on "past recipients".
Sometimes scale-ability can be a concern. Well-funded libraries with strong resources can do wonderful things, and it can be challenging for smaller libraries to keep pace. WebJunction's "Small Libraries Create Smart Spaces" page offers ideas for taking right-sized steps in smaller settings.