I could, yeah, but realistically, everyone enjoys different things, so it should perhaps be a list that all those taking part construct between them. What I will do is list what I do, which may give some ideas - I mean, the one that works for me best was actually something a friend does regularly, so I guess we can inspire each other.

As mentioned before, my current most effective (and I may add, quick) alternative to catatrophising is chanting. catatrophising may not sound like too bad a symptom, but it can lead to a complete meltdown for me. I experience my mental catastrophes, on an emotional level, as if they really happened, if I follow them long enough. It is then very hard to soothe myself and I start magical thinking, that they were somehow prophetic, and it would be dangerous to ignore them.

So, for the purposes of this post, I chant in my head or outloud (if not in public) when I catch myself catatrophising - just for however long it takes to feel better - sometimes within a minute.
I chant Nam-Myoho-Renge-Kyo. The heart of the lotus sutra. I chant every morning also.

My next most effective method is talk, write, or walk. In that order. I do benefit from verbalisation of what is bothering me (although I had to become accustomed to this through therapy), but there isn't always an appropriate person available, so I will then write - journal, song, poetry - sometimes that is not enough, so I will then walk. A difficult walk. Exertion usually helps me get back in my body and out my head, so I walk over uneven, steep hills - probably rambling more than walking.

Those are what work for me. I have been chanting for a few weeks, and it hasn't failed me once yet when I've employed it to overcome a symptom. The others though aren't always effective or appropriate to every situation.

It would be good to see others' methods, and so we could have a big list for people to chose from to get through their 24hr pledge.