Mount an .ISO file without burning a disk: This would come in handy. I find myself extracting ISOs to disk a lot.
A small Windows utility called the Virtual CD-ROM Control Panel can mount an .ISO disk image and access the files on it as if it were burned to CD or DVD.
I prefer Alcohol 120%, personally, but the problem is that it's a pay program and it's not exactly small. But it does support more formats than .ISO and it has other pretty features that come in handy.
I use Virtual CD-ROM all the time. It is the preferred method of using MSDN downloads rather than cutting to a disc.
Why not use Daemon Tools? http://www.daemon-tools.cc Free and understands all CD/DVD image files
I've been using one called CloneDrive for two years now. Definitely a handy utility.
I second the Alcohol 120% endorsement -- it also burns/creates/manages your disc images for you.
Sounds an awful lot like disk images on OS X, which is supported directly by the OS. That sort of thing has been around on the Mac since... oh, 1998 or earlier. I kinda assumed that Windows could do that also... No?
A disk image, created from a folder on the hard drive or any removable disk, can be mounted on the desktop and appear just like a removable disk. They can be read-only or read/write.
This is nothing new. It's been a part of Power Tools for years.
Handy? Yes. New? No.
Dave -- don't forget that Linux had it way before OS X. Keep your ego in check, many OS X fanboys are switching to Ubuntu.
All my boxes, save one, are Macs. The one is a gray box running Ubuntu.