Leshan Buddha – one full day
Emeishan – 2 days
Jiuzhaigou – 3 days
Those are all good places to check out. I would also suggest:
1. Qingcheng Mountain (the back mountain, houshan, is my favorite)
2. Dujiangyan (famous natural dam)
3. Sanshengxiang (aka Flower Town)
Western Sichuan is beautiful, too. Maybe Seabass will come in here and offer some more specific suggestions for that region, he knows it well.