I've been plowing through Discworld books like there was no tomorrow, and it's odd, but I think I read my favorites first. For those who don't know, the Discworld "series" is actually a bunch of smaller series just set in the same world. Here's a graphic that explains it.
I read the Watch books first and loved them. I then read the Rincewind books and thought they were generally good. Now, I'm reading the Death books, and the first two really seem to have the same premise, but they're still good. Still, that grouping is short, and then I'll read the Witches books. I've only read the first of them so far.
As a break, I started the first Dresden Files book, and I really like it so far.