USB Pen
Several months ago my son-in-law presented me with a 128mb flash memory device. The idea is to plug it in to a usb port and instantly get 128mb of quick, removeable, storage.
128mb is not really large enough to serve as a system device , but it is plenty to turn a marginal 64mb, memory limited machine into something useful.
Just use the usb flash as memory by assigning it the windows swap file location or make it the swap partition in a Linux application.
Works well and is just as good as adding an additional 128mb of ram.