Komodo Edit (Windows, Mac, Linux)

Komodo Edit is an open source application that has support for PHP, Python, Ruby, JavaScript, Perl, Tcl, XML, HTML 5 and CSS 3.

It has syntax coloring, folding, background syntax checking,  auto-complete and calltips. It also includes libraries for autocompletion for jQuery, Ext JS, Ruby on rails and more.

I just recommend Komoodo Edit.