I can too - I think I managed to teach myself to respond ticklishly to my own touch, somehow. I can tickle myself not just on my feet, but also on my ribcage and under my arms; it has more effect when I'm half asleep (probably 'cos I'm not thinking as clearly, so the signals are less effectively blocked, or somesuch).
It's kinda cool, 'cos I don't like to be tickled by other people (my family have learned over the years not to tickle me, the hard way. I react really violently to it - I don't know why though...).
Once or twice, I dreamt about tickling someone (a random dream-person, not anyone I know), and woke up laughing, as though I was the one being tickled. Weird.... :weird: