Admittedly these are unlikely to be useful for those of you who do your riding in Texas, Essex, Suffolk, Kent etc but for those of us in less blessed climates, these are the business.
I've come across so-called waterproof jods before but no others have actually done what they promised so I've always relied on overtrousers instead but these look much better and are much more comfortable.
They are manufactured by Townend and are made of softshell - full details here for the ladies' version: http://www.townendonline.co.uk/products/Townend-Shower-Proof-Fleece-Lined-Ladies-Breeches-.html
and here for the men's: http://www.townendonline.co.uk/products/Townend-Shower-Proof-Fleece-Lined-Mens-Breeches.html
They aren't cheap but if you spend a lot of time riding horses in the rain then I highly recommend them. Obviously you have to be a bit careful washing them - the label says you can use detergent but I don't trust that so I use Nikwax TechWash, which doesn't destroy the waterproofing.
I've now thown caution to the winds and bought myself a black pair for everyday. I got mine from this place, who were delightful to deal with and had one of the best prices at the time: http://clippityclobber.co.uk/shopping/mall/clippityclobber/Product/imp-softshell-ladies-winter-breeches-from-townend-ot5772-1239248
The only thing to beware of, if you are buying online, is that the legs are cut very narrow and the material isn't terribly elastic so unless you have very skinny legs you will need to buy a size bigger than normal, particularly if you want to wear thermals underneath. Alternatively, of course, just don't ride in terrible weather...(!)