For the iodine clock reaction there is a method of doing a titration - that I used - I cant remember what it was called unfortunately and it I no longer have a copy. I think it was done on the basis of performing the reaction and then stopping it by adding a certain chemical, although you must make sure it is quenched properly, after a set period of time, i.e 10 secs, 20 secs etc and then titrating this with another chemical to see how much of the iodine has reacted. This is however very time consuming - as you have to do the experiment at least three times for each length of time for each concentration/other variable and then you have to titrate each one.
Also word of advice - do your calculations all on excel in a nice table then copy and past into word - I didnt and payed for it dearly as one small mistake at the begining means you have to change everything! It may seem obvious now - but it wasnt at the time.