Pondering subseries and reading order

Just as a thought process, I was wondering about all the various subseries that exist within the Discworld universe.
I know there's a few for Moist Lipwig and the whole making money endeavor and one for Vimes and the Anhk Morpork (I know I'm spelling that one wrong) guards.

But what others exist?
And what order should these subseries be read? Or should they all be interwoven?

>1 gilroy: Discworld is one of those series where it's not strictly necessary to read the books in a particular order. The subseries can be read in whatever order strikes your fancy; there's crossover between them, but each subseries is independent enough to be read on it's own. When recommending Discworld I usually tell people to pick a subseries that looks interesting to them and start with one of the early books in it.

In addition to Moist von Lipwig and the City Watch, there's Rincewind (the first books, but not the place most people recommend starting), Witches, Death, Tiffany Aching, and several others; the Discworld series page has all of them listed in the related series section.

Personally I've always read the series in publication order. But that's a big undertaking.
This grapical illustration of the different routes through the series may be useful.

>3 Helenliz: I think I have an earlier version of that chart. I love it. Helpful in arranging the books on my shelves, also.