skEdit v4.0 ships with support for the following languages:
ASP
ColdFusion
CSS
HTML
MovableType
JavaScript
Perl
PHP
Python
Ruby
SQL
skEdit encapsulates all of the settings for a language into an OS X bundle, which is essentially a directory containing certain files in certain places. New languages can be added to skEdit by creating new bundles. The settings for a language can be modified in the Languages preference pane.
Each language bundle can specify which file categories and extensions it handles. When opening a matching file, skEdit will use that bundle. If desired, you can override that setting using the bundle-picker at the bottom of the editor. This setting will be persisted as part of the project.