Well, with ALMOST absolute certainty I think it was Dooku. I leave myself open to be surprised though in EPisode 3.
I highly disagree with the poster that said Sidious didn't plan the Clone Army that far in advance. First of all, Sidious/Palpatine, has had this planned for a long time and I think from the very beginning! Sids has plans from the beggining to be the Emperor, and he has it outlined in his head. He is patient and cunning! He knows he can't do it overnight, so he does it in steps, the first step was getting the Trade Fed to create a problem that would lead to a vote of no confidence to Chan. Valorum in the senate, once this happens he then can step in himself as Chan. after this he then leaves the Trade Fed to hang, as we found out in AOTC as to why Nute Gunray was unhappy! Now being Chancellor, he can start his second step to being empror, and thats creating in secret the CLoen Army, whiel it remains to be seen if he did the actaul ordering or had someone else do it, he was definitly behind it. If you look at the timeline of the movies and the dates that we are told in the movies, we know that the clone army was ordered almost immediatly after TPM, maybe een while it was going on! How do we knwo this? Well, we know that Sifo Dyas was killed approx ten years before the events of AOTC, and that AOTC took place 10 years after TPM, becasue in TPM Anakin was 9 and in AOTC he was approx 20. THen on top of that, there was a batch of Clonetroopers all ready for the republic to take control of and it took suprisingly 10 years to grom a batch of Clonetroopers! So with all that said, Palpatine/Sidious had to have this plan well in hand before the events of TPM, so that he could make sure it ran smoothly!