Giulio Caccini (circa 1545 - 1618) was an Italian composer during the Renaissance, and was associated with both the Medici family, and the Florentine Camerata -- a group of humanist intellectuals and musicians. Their interest in reviving classical Greek drama gave rise
to the modern opera. He was the musical director of the Medici court from 1600 until his death.
Caccini is best known as the inventor of the stile recitativo, or reciting style, a form of song used in opera. Caccini also developed a form of monody, where a single high voice sings an ornamented melody, accompanied by a bass harmony. This was a precursor to the baroque style. He wrote several love songs in this style,
which he collected into the book Le nuove musiche in 1602. He also wrote an opera, Euridice.
The Caccini Ave Maria has apparently seen a resurgence in popularity in recent years (I haven't heard
it yet), but his love songs are also particularly
well-known and are very beautiful. Examples can be found
on Live in Italy by Cecilia Bartoli.
Giulio was also the father of Francesca Caccini, who
was also a composer of operas at a time when such compositions by a woman would have been frowned upon. Apparently, she chose to call her work balleto rather
than opera to avoid embarassing her father.
Sources: www.classical.net, britannica.com, es.rice.edu/ES/humsoc/Galileo/Student_Work/Florence96/caccini.html, the Yale University library catalog, and
Cecilia Bartoli, Live in Italy (London/Decca CD 289 455 981-2).