20Gb of sleepimage OSX Mavericks
I had a similar problem. After waking my Macbook Pro from sleep, I found that space had magically diminished to just a few megabytes, even though I had several GB free before putting it to sleep. Deleting the sleepimage as suggested in the above post freed up the space again (the image had grown to about 4GB - pretty much the amount of space I was missing).