Programming languages supporting regular expressions (not an exhaustive list!):

  Tier 1 (syntax support):            Perl, Ruby
  Tier 2 (standard library support):  Python, Java, C#
  Tier 3 (external library support):  C++, C

UNIX utilities:  grep, sed, expr, etc.

Editors:  vi, vim, emacs, jedit, etc.

Integrated development environments:  netbeans, eclipse, etc.

Desktop environments:  KDE, Gnome, etc.