Well...we just had a SWTC trunk show at our LYS, and one of the items he had was a baby blanket made from Tofutsie. No pattern, but if you figure out the # of sts/inch, multiply that out to the size you want, you can do stocknette stich to the size you want; then crochet a lovely border arount it. It was BEAUTIFUL.
Another use for sock yarn I saw recently was a mitered squre blanket. It is going to be an adult sized blanket, an "heirloom". Each square was a different sock yarn, very tiny (maybe 2" x 2") and the girl who ws making it was using her yarn and trading with others on a knit-a-long site - sorry, but I don't know where. It was quite nice, but seemed time consuming.
Many of my knit friends are holding a strand of sock yarn with a DK or worsted weight and turning out some very unusual knit fabrics.