Programming languages
Expert: ( C/C++(STL, BOOST), Pascal, Delphi )
Average: ( PHP, Java, Python, C# )

Database
Expert: ( SQLITE )
Average: ( SQL, MySQL, Oracle(including PL/SQL) )

Frameworks & GUI
Expert: ( QT, VCL, FLTK )
Average: ( MFC, NET, wxWidget )

Scripts language
Expert: ( LUA )

Concepts
OOA/OOD/OOP
Design patterns
Multithread and synchronization
Network programming (ACE)