Another one to consider is http://searchcode.com/ It supports regex search as Google Code search does. For example,
http://searchco.de/?q=/[cb]at/
http://searchco.de/?q=/a{2,3}/
http://searchco.de/?q=/^import/
http://searchco.de/?q=/atoi/%20ext:c
http://searchco.de/?q=/dll$/
Are all valid searches.