Not sure about anyone else, but I love these types of products. I can use them with S&W, Runequest, and maybe even Traveller, depending on the supplement. I wish more companies produced these items.
Systemless books I own and recommend:
The Mother of All Treasure Tables by Necromancer Games - tons of non-magical treasures separated by value.
The Random Esoteric Creature Generator by James Raggi IV - weird monster creation. Kinda aimed at D&D clones, though.
Gary Gygax's Extraordinary Book of Names by Troll Lord Games - must-have book. Just lists of first and last names by culture. Also very good reference for authors.
Ultimate Toolbox by AEG - Just a big book of lists of all kinds of different subjects, from medicinal plants to city names and lots of other stuff.
Freeport books by Green Ronin - cool pirate setting. A bit more 1600's than I usually am willing to go, but great stuff.
I do have some other similar books, but these are the ones that stand out for me. I'd be interested in what other books are out there that I may not have heard of.