Languagey type stuff:
C
Java (swing, j2ee)
Scheme (sisc)
XML and XSLT
fop
javascript
html
Admin type stuff:
All manner of servlet containers and web servers (well just tomcat, jetty, apache, websphere, IIS)
amanda
sendmail
General linux and winblows admin stuff
Other stuff I do at work:
General hardware fixin'
Reading slashdot
EDIT: Forgot about databases
I have used postgres, db2, oracle, mysql, and am fairly fluent with the dialects of SQL they use.