Mumsnet can be an absolute cesspit of a forum as far as I'm concerned with endless opinionated high and mighty venomous bitching going on between many of its FMs, plus they have a fairly liberal attitude to F-bombs, which to me seems a bit incongruous for such a forum.
The other one, Netmums (which it probably often gets confused with) is much tamer by comparison.
I know I probably might be considered a bit of a weirdo for viewing such sites as an adult male, but it's usually when researching specific issues that concern me at the time, and the articles/threads on both of said sites were linked from Google.
Plus there are actually male posters on the Netmums forum despite said site's female-centric name.