There's always an old scope somewhere... a good ol' 20Mhz dual channel is still good enough for many purpose. Sure you can found one for ~50$ used. There's still some USB model available here and there... and finnally there's some PC card.

But.. hey wait a minute... sure you have a TV? You could try to build this one... based on PIC12F675
http://www.dos4ever.com/uscope/uscope_e.html

i always been amazed of that... never tested it though...yeah limited... but come on.. it's a PIC12F675!!!