Giacomo Leopardi kept between 1817 and 1832 notebooks. They are now usually referred to as "Zibaldone di pensieri" ("mixture," "unstructured collection" or "grab bag" of thoughts). In them, he recorded his ideas, notes, and excerpts about literary, moral, societal, and political matters. In 1832 he began to collect and revise some of these for a short book of aphorisms. But he died before they were published. The book was later published by his friend Ranieri under the title Pensieri di varia filosofia e di bella letteratura. The entire set of notebooks with its 4523 entries were later published as well. There is a pdf file of the 1921 edition. An interesting Hypertext edition in Italian of part of this book is available at the following Website Zibaldone di pensieri. The Leopardi Centre at the University of Birmingham has started the Zibaldone Project , which promises the first complete English edition and translation of this work. It is to appear in 2010.
This is significant, even if the working hypothesis of the project seems to me somewhat too grand. I am not sure that "the Zibaldone represents a new kind of 'book of memory' which is not accounted for by models of the past." Nor do I believe that "the Zibaldone embodies a characteristically modern way of conducting philosophical argument through a non-hierarchical discourse, the typical form of which is the fragment." If "Romantic" were to be substituted for "modern," we might get somewhere, even if not to "philosophical argument" in any strict sense. (And this is not meant as a criticism of Leopardi's original "Mischmasch" or "Sammelsurium" either, which, so far, I have read only in German.)
There is a translation into English: Giacomo Leopardi, Pensieri . Tr. W. S. Di Piero. Baton Rouge: Lousiana State University Press, 1981. This edition is said to contain English translations of all the pensieri , with the Italian text on facing pages.
Addendum: I got the book; and I found out that the translation actually does not contain the entire text of the Zibaldone, but only what Leopardi himself selected for publication shortly before he died (and what was published in the 1845 edition by Ranieri). It represents 111 of the 4526 notes.