Shasplit takes a large data block, splits it into smaller parts, and puts those parts into an SHA-based content-addressed store. Reassembling those parts is a trivial "cat" invocation. Repeating parts (e.g., from previous split operations) are stored only once, which allows efficient incremental backups of whole LVM snapshots via Rsync. Shasplit shows its strengths on encrypted block devices, but might be useful for non-encrypted data, too.
s6-portable-utils is a set of tiny general Unix utilities, often performing well-known tasks such as cut and grep, but optimized for simplicity and small size. They were designed for embedded systems and other constrained environments, but work everywhere. Other sets of small utilities are usually system-specific; for instance, the (otherwise excellent) BusyBox project only works on Linux.
minidb is a Python module that utilizes the SQLite3 database library in order to store and retrieve Python objects. It utilizes Python's __slots__ mechanism to determine the column names, and uses the class name for table names. Data is always stored as text in the database, but will be converted using the type specified in __slots__ (which therefore has to be a dict).
Werc is a minimalistic RESTful Web application framework and content management system. It follows the Unix "tool philosophy" and it is designed to be fast, simple, convenient, and easily extensible. It handles both small and big sites and has a flexible system for user and group permissions. All data is stored in plain text files that can be easily manipulated with standard tools, without using any databases or other external dependencies. Existing applications include a blogging engine with RSS/Atom feeds, a wiki system that can easily integrate pre-existing documents (can be enabled for any directory tree), and others.