I've recently had my first chils (DS, aged 10w) and have to say that the NCT in my area have been fantastic. I joined for the classes, at the recommendation of my boss (who is still in touch with her NCT group with her DS just celebrating his 18th!). I'm not from the UK, and don't have many friends with children who live nearby, so found it an excellent way to meet other mums-to-be.
Our course teacher was very good - patient, happy to run through all the alternatives for birth plans (we had two planned sections, who were given the support that they needed and plenty of information) and a visit from a breast feeding counsellor. We have all stayed in touch after the course, and been able to email/call/text when we have had questions. The mums now meet weekly to catch up, and it's been a great support network.
The new mums morning tea was a nice opportunity to meet others beyond our class group. I've attended the nearly new sales and picked up some excellent bits and pieces very cheaply. There are also often email messages going around which offer things outside of the sale periods (allowing me to get a while bunch of reuseable nappies in exchange for a donation to the branch)
But the thing that I'm really pleased to hear about is something which is just getting off the ground in our area at the moment, and that's an effort to support our local womens refuges by providing essentials for mothers in need. They have secured some corporate sponsorship, and together with branch volunteers and donations, are arranging for packs of necessities (ranging from nappies through to clothes/toys) to be available to support others. It's that sort of initiative which has impressed me more, and I think it's far too easy for people to knock the NCT as natural-birth/breastfeeding Gestapo without looking into some of the other things that they do... Support evenings at local hospitals, discussion groups and play sessions etc etc.
It's a totally personal thing, and YANBU to make your donations however you wish. But I'd certainly look into some of the stuff they do, and even if not making the monetary donation (though I'm sure it helps!) consider whether you'd like to support them through volunteering for some of the initiatives...