What I do.

I work for a University writing programs in Perl, most of which happen to have a web based user interface. This is subtly different from writing Web Sites. Also, I use Perl for data transforming and analysis etc. Some ot the programs have a Perl/Tk interface and the ones for me have a command line interface and some have a context sensitive user interface.

In addition, I use PostgreSQL for database and Linux to run the box. My only non open source interaction is with a PC that I run VNCviewer on (i.e. its an X terminal basically)

In short, jobs where you do 99% open source stuff are out there. Working for a non-corporation does limit the cash inflow slightly but the environment is a lot easier going and much lower stress. (I came from doing Senior System Admin for a corporation).