Yep. It all depends on the operating system though. You can get a solid state hard drive for just the OS and swap file. Then, put your programs, etc, and a regular hard drive.
Or, you can get an ACPI motherboard, and load the proper ACPI drivers for your OS, and turn it on and off with the power switch. It takes about 5 seconds for it to come back up. It takes all the stuff in RAM, and puts it on the hard drive. Once you power it back up, it takes that info on the hard drive and puts it back into RAM like it was always there.
I have built a few computers with WindowsME that do that. It's great for kids that don't know how to properly shut down the system.
