I am not sure if this is a resource that is known and used by those who, like me, are not specializing in Deleuze, but there are some of Deleuze’s lectures available in transcription (both in French and English) here. There are several lectures devoted to Leibniz and I think they clearly show Deleuze’s appreciation of Leibniz, a sort of a personal appreciation as opposed to the “official” mention or engagement. This is from the very first lecture on Leibniz (4/15/1980):
To begin reading Leibniz, there is an incomparable working instrument. It is the life work, a very modest work, but a very profound one. It is by a lady, Madame[Lucy] Prenant, who had long ago published selected excerpts by Leibniz. Usually a collection of excerpts is of doubtful value, but this one is a work of art, for a very simple reason: Leibniz had writing techniques which no doubt were rather frequent during his era (beginning 18th century), but that he pushed to an extraordinary extent…
I want to say very quickly how I recognize a philosopher in his activity. One can only confront these activities as a function of what they create and of their mode of creation. One must ask, what does a woodworker create? What does a musician create? For me, a philosopher is someone who creates concepts. This implies many things: that the concept is something to be created, that the concept is the product of a creation.
Deleuze compares philosophical activity to an art of musical composition – something I have always felt was a great analogy, even if somewhat obvious – with Deleuze, however, this analogy receives an interesting twist in terms of its defining reference to the idea of the flow:
A concept is not at all something that is a given. Moreover, a concept is not the same thing as thought: one can very well think without concepts, and everyone who does not do philosophy still thinks, I believe, but does not think through concepts. If you accept the idea of a concept as the product of an activity or an original creation….
For me, there are as many creations in the invention of a concept as in the creation by a great painter or musician. One can also conceive of a continuous acoustic flow (perhaps that is only an idea, but it matters little if this idea is justified) that traverses the world and that even encompasses silence. A musician is someone who appropriates something from this flow: notes? Aggregates of notes? No? What will we call the new sound from a musician? You sense then that it is not simply a question of the system of notes. It’s the same thing for a philosopher, it is simply a question of creating concepts rather than sounds.
There is much more interesting stuff on Leibniz in these lectures – take a look…