Berkeley DB (libdb) is a programmatic toolkit that provides embedded database support for both traditional and client/server applications. It includes b+tree, queue, extended linear hashing, fixed, and variable-length record access methods, transactions, locking, logging, shared memory caching, database recovery, and replication for highly available systems. DB supports C, C++, C#, Java, PHP, and Perl APIs. It supports key-value pair (NoSQL), SQL, and Java Object formatted data. It is available for a wide variety of Unix platforms as well as QNX, Android, Mac OS X, and several varieties of Windows.
Boa Constructor is a cross-platform RAD GUI-building IDE. It offers visual frame creation and manipulation, an object inspector, a debugger, integrated help, and many views on the source, including inheritance hierarchies, object methods and properties, and HTML generated from documentation strings. It is written in Python and uses the wxPython toolkit which wraps wxWindows.
The Cacheability Engine will check a URL you feed it for several things that will affect a Web cache, including web server clock skew, expires and Cache-Control headers, Last-Modified date presence, validation of LM date, Content-Length presence and more. It makes it easy to see how a cache will treat your content. There are also public engines running, so you don't have to install the software to use it for Internet-available sites.