USB thumb drive as swap
There are howtos and scripts which lets you use a USB flash drive as swap partation. It is easy to do, make a normal swap partation, run swapon and make sure you do not remove the USB stick.
But do consider these facts:
hdparm -t -T on a random slower SATA harddrive are:
Timing buffered disk reads: 256 MB in 3.11 seconds = 82.42 MB/sec
And a 1 GB USB 2.0 drive:
Timing buffered disk reads: 58 MB in 3.09 seconds = 18.75 MB/sec
Yes. USB attached drives are mostly slower. Your numbers may vary, and good luck, but do note that it's a bad idea.