Gaby is a small personal database manager using GTK+ and GNOME (if available) for its GUI. It was designed to provide straight-forward access to the types of databases a casual user would normally use, while keeping the ability to easily create databases for other needs. It was designed with extensibility in mind and relies heavily on plug-ins.
ToutDoux is a project manager for GNOME. The approach of data manipulation is abstract (database free). It's extensible with plugins. Most tasks are and will be subcontracted with commandline frontends. The file format is XML (including a schema, plugins parameters, and datatables).
Copper is the feature-wise Linux port of the Windows-only software Golden32 by Benthic. It allows developers to view data in a table format rather than in SQLplus, and lets you do select, insert, update, delete, commit, and rollback. It supports Oracle and MySql, and features a tabbed view to manager your queries, syntax highlighting, right-click updates, and a table/column browser.
gnome-courier is a collection of programs for courier services. It includes programs for managing clients, managing coworkers, managing jobs (receiving, distributing, and editing), printing bills and overdue notices, and managing the payroll. Various statistical modules are available, and since the project is based on a modular concept, it can easily be extended.
DWI, Data With Interaction, is an Object-to-Relational Mapping (ORM)-based RAD (Rapid Application Development) system for rapidly creating data-driven desktop GUI applications. It maps SQL tables into several object systems, including QOF, GLib GObjects, and GTK/GNOME. It can be used with the Glade GUI designer. It supports multiple databases through ODBC and libdbi.
Alexandria is a GNOME application to help manage a book collection. It retrieves book information (including cover pictures) from several online libraries, allows you to search for a book (either by EAN/ISBN, title, authors, or keyword), can import and export data into ONIX, Tellico, and EAN/ISBN-list formats, generates Web pages from your libraries, allows marking your books as loaned, saves data using the YAML format, features an HIG-compliant user interface, shows books in different views that can be filtered or sorted, and handles book rating and notes.
Network-config is a simple and easy to use program that helps in configuring the network interfaces for Linux-based operating systems. It allows you to have multiple configurations for the same computer, and to easily configure NAT for Internet sharing. It can also be used to scan for wireless networks. It is written in Perl and uses GTK2+, but also works as a command line program.