Tools
Recording
Tools for recording UTAU voicebanks.
Recstar 
By sdercolin.
- Has GuideBGM support
- Cross-platform (Windows, Mac, Linux)
OREMO
By nwp8861
No longer maintained.
- Has GuideBGM support
- Cross-platform (Windows, Mac)
Mac build is broken
akorin
By KLAD. Crossplatform OREMO alternative.
No longer maintained in favor of Recstar.
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For OSes other than Windows, you must build it from source.
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No GuideBGM support.
aie
By team-aie.
No longer maintained.
Bokumo
By kylejlin. Web browser alternative.
RecBoard
By KoharuYuzuki.
Vocalist
By oookamitai
- MacOS only
Rekuta
By atouu
- Android only
OTO Configuration
Tools for configuring UTAU voicebanks.
vLabeler
By sdercolin. In development.
SetParam
By nwp8861.
WavConfigTool
By Heiden.BZR.
Snatcit
By kylejlin. Web browser alternative.
mkototemp (MakeOtoTemp)
By Delta. Automatically generates oto.ini for CVVC voicebanks. May require configuration.
Mediafire (Stable)
GitHub (Latest)
KiraOtoToolbox
By shine_5402. Various tools for editing the oto.ini.
oto.iniまとめて改造ましーん
By まいこ. Various tools for editing the oto.ini. Japanese only.
Other
UTAU TextEncode Convert Helper
Original by mili-tan, Forked by TUBS.
Converts voicebanks and USTs to and from Chinese(GB2312), Japanese(Shift_JIS), and UTF-8 encoding.
Speedwagon
By Custom.Maid. Software for quickly regenerating frqs.
VocalShifter
By Ackie Sound. Vocal editor that can edit pitch, DYN(Dynamics), formant, pan, timing, etc.
MinimizeVB
By アステル. Minimizes the file size of a voicebank before distribution and makes an installer.
OpenUtau-Dictionary-Editor
By Cadlaxa