People might laugh at you for putting gaffer tape on a split or damaged tyre, but check this out - it actually lasts a lot longer than you'd think.
This tape was applied top of St Helena trail in The Oaks and here you see the result when we got back in to Glenbrook (about 13Km later). There was also a temporary fix inside the tyre which I noticed was giving way when I took it off to replace it, so it's quiet possible the gaffer tape saved the day.
P.S. What do you mean, "Where did you get the tape?", you mean you don't carry some in your backpack always 
What if I don't have gaffer tape?
If you don't have gaffer tape or would prefer to keep it for use at quieter moments there is another trick. Take your tube out, partially inflate it till it takes shape, wrap an aussie five, ten, twenty or fifty dollar note around the tube, denomination used will depend on whether you are married with kids or single. Put the tube back inside the tyre, lining the note up with the gash in the tyre and fit it back to your rim. Pump the tyre back up and off you go.
Yes it will probably cost you the after ride coffee but the good old plastic aussie dollar is finally good for something.
Happy trails