Ootake - A freeware emulator for Windows. - http://www.ouma.jp/ootake/
GPengine - A full speed PCengine emulator for GamePark's GP32 handheld. - http://www.gp32x.com/gpengine/
RiscPCE - An old, open source emulator for RiscOS. Maintained by Paul Clifford. - http://www.plasma.demon.co.uk/pcengine/pce.html
TGEmu - An open source emulator for BeOS, DOS, MacOS and Windows. Maintained by Charles McDonald. - http://cgfm2.emuviews.com/
Magic Engine - A shareware emulator for DOS, MacOS and Windows. Supports any HE System, from CoreGrafx to Arcade CD-ROM. Maintained by David and Cédric Michel. - http://magicengine.com/