UTAForum
The largest (and one of the oldest) forums for overseas UTAU users.

UTAU Wiki
UTAU voicebank database.

UTAU Wiki 2.0
UTAU voicebank database; successor to the UTAU Wiki.

utau2008 utau-synth
Offical UTAU websites administered by Ameya.

UTAU N.H.P (中の人をプロデュース)
One of the first UTAU tutorial websites. Made in 2010 and was shut down in 2012, but has came back online due to an archive hosted on utau.us.

UTAU DB
UTAU voicebank database similar to the UTAU Wiki. Also contains various tutorials on UTAU.

UTAU User Wiki
UTAU User wiki that covers a range of UTAU topics, much like utau.us.

UTAU Voicebank Making Wiki
A wiki on voicebank making; contains links to many resources such as reclists, guide BGMs, etc.

UTAU Naver Cafe
Korean language UTAU forum.

Korean UTAU Wiki
Korean language UTAU wiki; also contains tutorials.

Haru's UTAU Tutorial Station
A Chinese language UTAU tutorial site run by Haru.jpg.

Chinese UTAU Wiki
A Japanese language wiki for Chinese UTAU only; also has a Chinese language version.