We were recently looking for an open source light-weight database web administration tool that would be preferably database cross-platform and would work on either ASP.NET or PHP. Adminer fit the bill.
Adminer is written in PHP.
It supports, out of the box PostgreSQL, MySQL, SQLite2 and SQLite3, and even SQL Server and Oracle. This covers most of the databases we commonly use.
Here we'll go over some other features we liked about it that are rare in other web database administration tools.
If you are on windows, the PostGIS 2.1 window binary builds get built whenever there is a change in PostGIS 2.1 code base by Winnie our windows PostGIS build bot, for PostgreSQL 9.0-9.2 (64-bit) and 9.2 (32-bit), so you can't use the I can't compile excuse if you are on windows, not to test out the new changes :). You can download these from Windows Experimental Builds. We are hoping to do the same for Debian Squeeze (6) soon. The main reason we built our bot Debbie on Debian (which makes the source tarballs), is because Debian is a very popular deployment platform for PostGIS, that is currently underserved so we have many Debian users frustrated at not having a readily available PostGIS 2.0 release for example.