TOra is a Toolkit for Oracle which aims to help the DBA or developer of database application. Features PL/SQL debugger, SQL worksheet with syntax highlighting, DB browser and a comprehensive set of DBA tools.
globecom.net/tora
sourceforge.net/projects/tora

Aqua Data Studio 3.7 is a database query and administration tool that allows developers to easily create, edit, and execute SQL scripts, as well as browse and visually modify database structures. Aqua Data Studio provides an integrated database environment with a single consistent interface to all major relational databases. This allows the database administrator or developer to tackle multiple tasks simultaneously from one application.
aquafold.com

Oracletool is an interactive, web based application that runs as a CGI script using your web server. The advantage of Oracletool over non web based tools is that nothing needs to be installed on the client side machine. All you need to use Oracletool, once installed, is a web browser. There is nothing that needs to be created or altered in your databases to use Oracletool either, other than a role for users who are not DBA's, but want to use the tool. No database changes whatsoever are needed for a DBA to use Oracletool.
oracletool.com

Quest Software presents Data Dictionary for Oracle v2.0, a freeware tool for viewing DBA_View and V$ View information. Use this application to reference Oracle 9.i2 documentation or connect to your own Oracle instance to obtain descriptions and column data from a live system.
quest-pipelines.com/..

more Oracle resources:
http://www.pcvoyager.com/dir/database_oracle.html