Squarebase is a Web-based interface for MySQL databases. The basic idea is that it builds a database (called the "metabase") that describes the structure of the database. The information in the metabase is used to format lists and forms for browsing and editing the contents of the database.
phpLiteAdmin is a Web-based database admin tool with support for SQLite 2 and 3. It consists of a single 60KB source file that can simply be dropped into a directory on your server and then visited in a browser. There is virtually no setup required except for specifying your database(s). The available operations, feature set, interface, and user experience is comparable to phpMyAdmin for MySQL.
Spaghetti Parenthesis Visualizer is an in-browser (meaning that it doesn't send your code to a server) tool that takes deeply nested conditionals in languages that follow in C's footsteps, including Python, Perl, PHP, and Java, SQL queries, or some Lisp code, and provides two visual presentations that clearly and cleanly display how deep each part of the code is in the layers of nesting.