I'm sorry I was mistaken, a 555 will not produce a triangle wave. I was looking at the datasheet, and on a graph, I saw a triangle wave, but didn't realize that it was actually the RC network charging and discharging.
BUT, I see no reason why you couldn't use the RC network as an output. Of course it wouldn't be a perfect triangle wave, as a capacitor charges very fast at first, then slower. It would also have to be buffered, as any load would change the value of the RC network.
Or I'm sure there's an easy way of taking the square wave output of the 555 and changing it to a triangle wave. Whichever is less complicated.