For lighttpd, try the following in your config to log in a format identifical to that of Apache's combined log format.

    accesslog.format = "%h %V %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" 

See the docs on ModAccessLog for more information: http://redmine.lighttpd.net/wiki/1/Docs:ModAccesslog

as hoop suggested, it can parse Apache's combined format :-) And the contribution is welcome!