Originally considered Vocaloids as well, UTAUloids refers to voice banks that work on UTAU. This is done to differentiate them from Vocaloids that run on Yamaha's Vocaloid and Vocaloid2 platform. Because UTAU has the ability to manually import voice sounds as WAV files, it is quite easy to create "our own" Utauloids- which has resulted in a large boom of voice banks.
Teto Kasane and Ruko Yokune belong as UTAUloids, though their creators from vip@2ch attempted to pass them off as real Vocaloids, mostly for fun.
To see a somewhat-complete list of UTAUloids, visit this wiki: UTAUloids