This is a subject close to my heart! We have used cloth nappies on both kids, my youngest is still in them. There are literally thousands of different types available. Places like http://www.funkymonkeypants.com
(both UK sites) have good selections of the most popular types. HOWEVER, modern cloth nappies probably aren't the best solution in a SHTF situation. Modern fabrics like microfibre are very difficult to rinse properly by hand (I have tried it), which leads to trapped detergent and trapped bacteria, and many nappies are several layers thick, which makes them both difficult to clean properly by hand and very slow to dry. A much better option is the traditional cotton terry square which can be bleached and boiled if necessary. It's basic but very cheap, easy to wash, quick to dry and can be folded to fit any size of baby or toddler if you get the standard size ones. Forget plastic pants and get some good quality 'one size' wraps like Blueberry Coveralls, add some traditional pins or the safer 'nappy nippas' and you're sorted. Terries can be used for loads of things after nappies too. Don't stop at nappies, get cloth wipes too... and 'family cloth' if you're brave
A good place for washable feminine supplies is femininewear.co.uk. Again, loads of different pads available but cups are probably the better option if the water and electricity are off.
With nappies and feminine products, I would use them for at least a few months before needing to. Same as anything, you don't just learn a skill by reading about it and there is skill involved in both, or at least different methods you need to use than using disposables.