Syntax highlight source code within QuickLook
I use QuickLook constantly for everything from pictures, movies, text files, and of course, source code. Source can be a pain to view in QuickLook because there’s no syntax highlighting by default, but this plugin changes that. QLColorCode is a must-have QuickLook plugin for developers, it allows color syntax highlighting of nearly any type of source code from directly within QuickLook, making a quick glance at code infinitely easier. It’s free so download it now, you’ll thank me later.
Installation is simple, drop the plugin into ~/Library/QuickLook/ and restart the Finder and you’re good to go!

I have syntax highlighting on Snow Leopard.. I think this is more relevant for Leopard (10.5) only..
SL here too, with syntax highlighting by system default!
[...] | OS X Daily Más información | QLColorCode Google Code Descargar | QLColorCode Plugin En Applesfera | [...]
For those who say Snow Leopard (or later) has syntax highlighting by default, this is true, but only with certain languages that Xcode 3.2 and later knows how to highlight. Anything besides C, Obj-C, etc. (such as Python, Perl, many others) will NOT be highlighted. Therefore, this QL plugin is still VERY much relevant.