One metric I've seen is gzip-compressed size, which has the nice property that it identifies the size of the incompressible elements -- ie it discounts repetitive boilerplate.
Another interesting set of metrics is Halstead's "software science" metrics[1]. They fell out of favour because initially they were hard to count and didn't seem to correlate with anything else.
[1] http://en.wikipedia.org/wiki/Halstead_complexity_measures