Miscellaneous Container Templates is a C++ library that provides a collection of various STL-like containers with specific properties. It currently contains six closely related containers: closed_hash_set, closed_hash_map, linked_hash_*, and forward_hash_*. The first two are very similar to TR1 unordered_set and unordered_map; the linked ones provide additional functionality, while forward hash tables are more performant than linked, but have a restricted interface.
Analog PHP is a short and simple logging package for PHP 5.3+ based around the idea of using closures for configurability and extensibility. It functions as a static class, but you can completely control the handling of log messages through closures (aka anonymous functions), and it also comes with a dozen pre-written handlers. It is well-documented, with examples for each type of log handler, and ultra-concise. The core is literally only 43 lines of clear, non-obfuscated code, and the whole is only a fraction of the size of comparable packages (for example, 293 total lines vs 1021 for Monolog).