As with most films, there is a LOT of memorabilia around for the Mad Max trilogy. There are basically two types of memorabilia. Firstly there are the licensed items which were available for sale to the general public, such as the novels, movie programs, souvenir magazines, t-shirts, stickers, and so on. Then there are the promotional items, such as posters, lobby cards, press kits, press books, advertising layouts, and more. While promotional items (in general) were never sold directly to the general public, you can buy a lot of them these days if you look around at the various memorabilia and movie shops.
As you've probably guessed, I've collected quite a lot of Mad Max memorabilia myself over the years. You won't find a complete index of everything I have within my Mad Max web page however, it's a fairly time consuming task to photograph everything and put listings online, and I have enough trouble keeping up with the rest of the page sometimes! Instead I've left that up to Chad Maggio, who has put together his own comprehensive Mad Max memorabilia web site.
Of course I'm still happy to help you out if you've got a question, so feel free to contact me. If there's something your looking at buying and need further info, I'll do my best to help you out if I can. I might also be able to help you locate particular items, including a few I have spare myself. Alternatively if you're selling some Mad Max memorabilia, I might be able to help you out there as well.