DAEMON Tools is a virtual CD, DVD and HD DVD emulator software for mounting virtual disk images.

WinCDEmu is an open-source CD and DVD emulator for Windows which supports ISO, CUE, BIN/RAW/IMG file formats as well as SMB network shares.

MagicISO or MagicISO Maker is a CD/DVD image shareware utility that can extract, edit, create, and burn disc image files.

ImDisk Toolkit for Windows lets you mount image files of hard drive, CD-ROM and create RamDisks with various parameters.

OSFMount allows you to mount local disk image files (bit-for-bit copies of a disk partition) in Windows with a drive letter.

Virtual CloneDrive is a great tool for creating virtual ISO images.

PowerISO is a disk image utility that can open, burn, create, edit, compress, encrypt, mount and extract ISO files.

ImDisk is a virtual disk driver for Windows.

MobaLiveCD is a freeware that will run your Linux LiveCD on Windows thanks to the excellent emulator called "Qemu".