I worked on a big (200K+ line) CGI application for EOSDIS back when (around 1997) - wow, it's still in service! Essentially it was a search engine for earth science data. Not mission critical, but pretty critical to the scientists finding the data they needed.

A lot of fun, that project. If you want a peek at it (it's open to the public), it's called WIST (the Warehouse Inventory Search Tool). The one thing which is pretty cool there is the notification calendar on the front page, which is essentially a wiki that displays data based on the time range you assign to it.

That was code of my own that I gave to NASA for the project; I probably should see about redoing it with the benefit of another 10 years of experience.