Tell us more - we like a good disaster story on here!
Bit of a wierd one to be honest, cycling into work and after about 6 miles the chain started slipping all the time. I thought well only a couple of miles to go so I'll just put up with it. On a short steep uphill stretch when I was out the saddle there was a sudden bang, snap, crash and I came quickly to a halt. The rear mech was twsited in with chain, cable and housing all wrapped round the spokes of the rear wheel.

I think the chain snapped at the link pin and one of the links somehow got bent out at a 90deg angle, caught in the rearmech snapping it off at the mech hanger and throwing it all into the rear spokes whilst tearing apart the cable housing for good measure. The rear stays got a right good bashing too.
I untangled the mess and hobby-horsed it to the office.
Later during repairs I also found the chain was twisted too. Just glad it happened at 8mph uphill rather than 30 odd downhill

Anyway, repairs done - I'll cycle it in tomorrow and check it out.