Was mucking around today in Skype, and discovered that US toll-free number can be called without signing up for SkypeOut.
I tested several numbers, including the IE7 Beta 2 hotline (but they were asleep...) and it worked perfectly. So I tried the 1-800-FREE-411 number and it works. This is some sort of computerised directory assistance number that is toll free. Haven't tried a request yet but it should work. If it doesn't recoginse your voice after 20 secs or so you a directed to a real person. (Prank calls anyone? Should ask for a Mr. Bill Gates...)
Trying to think of other numbers to call... maybe Pizza Hut or McDonalds?