The official UTAU releases

A fan open source successor to UTAU

The loveable twin-drill chimera

A soft adult-like voice.

*Also has a Synthesizer V bank

A voice created with only sound and noise in Audacity. (I think??)

Powerful and deep male voice. He has both English and Japanese banks

Powerful male voice with large vocal range.

*If you are experiencing problems with him go here.

A very versatile resampler that works well with almost any bank.

Includes many useful flags including:
Mt - Makes the voice softer or more powerful

MG - Adds a growl

MC - Makes the voice course.

Can strengthen a voice and remove some background noise.

A complete tutorial for UTAU by Whologist