The other option would be to get a few of the Gigabyte i-RAM boxes and RAID0 them. They're basically a hardware solution to a RAM drive - a 5.25" drive bay box that stores up to 4x DDR 1GB sticks. There are a few youtube videos of people loading Windows or games on a 4x i-RAM box RAID0 array for a 16GB disk that is blazing fast..
The downside though.. for some reason, Gigabyte decided to use SATA 1.5Gb/s instead of SATA 3.0Gb/s and DDR instead of DDR2 modules, and DDR2 are a bit less expensive. Also, only 4GB per box? Ouch.
Considering each box is around $125, and 4x 1GB DDR sticks is around $110 (instead of $75 for DDR2).. that's close to $1k for a 16GB RAID0 array. Plus, you're probably going to want an external raid controller for either this or your main hard drives.. so add more to the cost.

Gigabyte in 2006 showed off a DDR2 8GB SATA 3Gb/s model.. but it was never released. I'm still waiting for it.