Awesome QuickLook plugins that are free. QuickLook shows previews in MacOS X Leopard. These plugins extend its capabilities. As a web developer, I find these quite useful. To install them, put the *.qlgenerator files in ~/Library/QuickLook (which folder you might have to create).
Archive plugin: previews the contents of zip and tar.gz/tgz archives.
Home page [in Japanese]: http://homepage.mac.com/xdd/software/archive/
Direct download link: http://homepage.mac.com/xdd/software/archive/download/Archive.qlgenerator01.zip
Folder plugin: previews the contents of folders.
Home page [in Japanese]: http://homepage.mac.com/xdd/software/folder/
Direct download link: http://homepage.mac.com/xdd/software/folder/download/Folder.qlgenerator03.zip
FLV plugin: previews Flash video.
Home page [in Japanese]: http://homepage.mac.com/xdd/software/flv/
Direct download link: http://homepage.mac.com/xdd/software/flv/download/flv_qlg01.zip
Color Code plugin: previews source code with syntax coloring.
Home page: http://code.google.com/p/qlcolorcode/
Direct download: http://qlcolorcode.googlecode.com/files/QLColorCode-1.1.0.tgz