We used Open Source software as much as possible while building these pages. The original version of IRDIAC was built with a combination of Java servlets and Java Server Pages on top of Apache and Tomcat. Information about our images was stored in a MySQL database, but the images themselves were stored in the filesystem.
Then we learned about UMN MapServer and built a few map-based pages with PHP and MapScript. This is the direction we have taken ever since. All new dynamic pages are built with PHP and we're in the process of rewriting the Java-based pages in PHP.
We have also started using the PostgreSQL database server in order to take advantage of the PostGIS extension and its interface with MapServer. As part of the Java-to-PHP switch, the database will be converted to Postgres in order to facilitate the use of more spatial data.
In addition, we also use some of the GDAL utilities and some custom Python and C code that use the GDAL and OGR libraries for some of the data processing that happens dynamically. We also use some code written in IDL with the ENVI libraries for some of this processing.
Open Source Web servers
Apache HTTP Server Project - web serverOpen Source Database servers
PostgreSQL - database serverFree or Open Source programming/scripting languages and libraries
PHPFree or Open Source Geospatial Software
MapServer - tool for building geospatial web applicationsCommercial Software
IDL - Language great for processing raster data