.. Official Pages
makusonia [S-JIS] - Official website for okui, masami.
MaBIC [S-JIS] - Website for the okui, masami official fanclub.
evolution-m [S-JIS] - Official website for Okui Masami's independent record label, evolution.
O-live [S-JIS] - Official website for Okui Masami's ongoing radio program on Animelomix, O-live.
JAM PROJECT Official Site [S-JIS] - Official website for JAM PROJECT, including discography/timeline of public appearances and releases, member information, tour goods, and more.
StarChild [S-JIS] - CD company, has a link to makusonia and sections on singers Megumi Hayashibara, Yui Horie, & Manami Komori.
KING RECORDS [S-JIS] - Music company website. There is an individual section on Makkun here.
r.o.r/s [S-JIS] - Starchild's r.o.r/s page. Well-designed page with videos, photo gallery, and information about this limited-time pairing-up of Okui Masami and Yonekura Chihiro.

.. Fan Pages
Avenue to Mac-kun [S-JIS] - Has an introduction, recent news, a pretty lively bulletin board / forum, discography, and links.
crossroad - Kata's newsblog has changed servers and also its layout into a website with very rare Makkun photos, postcards, and even autographed material. Also includes information, links, and other Makkun goodies.
We are JAM Project!! (JAM Project Fan) [S-JIS] - A nice fansite for this eight-member "Japanese Animationsong Makers" group. Includes song info database and more.
Makkun... Spirit of the Sunflower - Terrific English website, has discography, album reviews and rankings, a really interesting opinions page, downloads, and info concerning the anime series for which Makkun has done work.
okui, masami forum - mmc+ - A forum devoted to discussion of Makkun and music. You are required to register before you can post, but registration is fairly painless and quick, so please join in and add your voice to our dicussions!
Masami Okui Fanlisting - A fanlisting devoted to Makkun.