As I've been using, and recommending, Parallels Desktop more frequently as a way to run Windows on Intel-based Macs, the question of how to back up, move, delete, and otherwise manage Parallels virtual machines has come up regularly. One utility designed to address this need is BriteMac's $15 VM2Go, a 1.5 MB download.
At its most basic level, VM2Go copies virtual machines - which comprise at minimum a configuration file and one or more disk images - to another volume (another hard disk, an iPod, a USB flash drive, or a DVD). Obviously, since we're talking about a grand total of as few as two files, you can easily do the same thing in the Finder or in any backup program. However, VM2Go does a few other things that make it more useful than it might appear at first blush.
For one thing, VM2Go almost instantly finds, and lists, all your Parallels virtual machines on any mounted volume. If you have many virtual machines, if you've stored them in nonstandard locations, or if you've lost track of where they are, this is a handy way to locate them all. Furthermore, if you manually move a virtual machine from one location to another, in some situations it won't run from the new location because the old, no-longer valid path to the disk image is hard-coded into the configuration file. VM2Go automatically corrects this, when necessary, so you don't need to edit the file yourself to reflect the new disk image location. VM2Go also provides an easy way to delete all the pieces of a Parallels virtual machine (including a Desktop icon, if any).
The current version of VM2Go, 1.22, only partially supports the just-released Parallels Desktop 3.0. That is to say, it'll copy the configuration file and disk images just fine, but it doesn't yet know how to handle new features such as Snapshots, and can't correctly report the size of disk images formatted for Parallels Desktop 3. The developer says that a new version, which will correct these and other issues, is under development, with an expected release in the next several weeks.
At the moment, VM2Go is most useful for people with more than one Parallels virtual machine - and the more of them you have, the more useful it becomes. (If you have just one virtual machine, it seems to me that copying the appropriate files in the Finder is simple enough that you should save your $15.) On the other hand, the more virtual machines you have, the more likely you are to be highly technically proficient, and therefore outside VM2Go's target market. Still, I could foresee being much more enthusiastic about VM2Go in the future if it also supported VMware Fusion virtual machines (something the developer says he's looking into), if it could split backups across more than one DVD, or if it could create additive incremental archives of virtual machines - automatically backing up only the changed bytes of a virtual machine's disk image on each run (rather than copying the whole file every time). The combination of all those capabilities would make for a truly interesting utility.