Porcupine is an open-source Python based web application server that provides front-end and back-end revolutionary technologies for building modern data-centric Web 2.0 applications.
Infra-Red is a package of scripts designed to set up a service oriented architecture in PHP. It includes the server with an example service, a client library for the codeigniter framework and a stand alone client library.
phleackr is a PHP binding for the Flickr API, using the XML-RPC format and thought to be compatible with PHP4 and PHP5, while avoiding the need for PEAR packages. in the future it will also support the REST format.
PHP-O-Lait is a library that, in 2 boiler-plate lines of code, allows you to call server-side PHP code from client-side JavaScript. It's so easy, in fact, that you don't need to know how it does it (hint, it uses Ajax and JSON).
...PowerBlog was a powerful and intuitive Windows desktop blogging application. One could post blog entries to an XML-RPC/Blogger API host, FTP host, or other host. It was extensible using .NET assemblies or by using VBScript/JScript scripts. It had an Outlook-style article browsing interface.
PowerBlog's closest competitor was w.Bloggar until Microsoft Live Writer was released, which made PowerBlog an irrelevant product.
If you are curious about PowerBlog's author and what he is up to, visit http://www.jondavis.net/techblog Feel free to send Jon a message at jon -AT- jondavis-dot-net (<< anti-spam) asking him what he's been up to with blogging solutions lately.
Ajax.NET is an implementation of the AJAX technology used by Google, Orkut, Flickr, ... for the .NET environment. Call server side methods as if they were on the clientside.