OOoLilyPond (OLy) is an Extension for OpenOffice.org and LibreOffice. With OLy, you can include musical notation within text and presentation documents. The music expressions are entered as text codes and translated to images (png or eps) using LilyPond.
The development has moved to GitHub (https://github.com/openlilylib/LO-ly). You will not find new releases here anymore.
March 2015: On OpenOffice 18.104.22.168 (Linux), this works. The caveat is that the installer does not work. The libraries are stable, though, and integrates well with Lilypond 2.18.2 (current stable).
I've got it to work well in NeoOffice 3.x on OS X 10.4.11 ... see the forum threads for fixes.