OK, these guys are not a reenacting vendor of any sort, but they have a unique collection of publications for the reenactor, wargamer or militaria freak in general. Lulu was mentioned in a seminar at my work, and it turned out to be quite a resource for history geeks like me.
What makes it cool is the fact that Lulu caters to people who self-publish. So what you see is the stuff that normally doesn't find its way to a bookstore. But then again, that is one of its inherit dangers, too. Searches on reenactment, wargame and similar turn up some interesting titles.
Another wish of mine would be to see some enterprising soul publish some home-grown stuff and make it available via Lulu. Republished drill manuals would be perfect, as would be period tracts, booklets and other things that reenactors would need to round out an impression.
Well worth your time to browse the site.