Where should I save the uploaded Pictures? And how do I resize pictures?

Hi, I have many pictures using in my web, and most of pictures will be uploaded by users. Those pictures are products pictures and user's blog pictures.
I thought about 4 ways to save those pictures:
1) to create two folders: products and blogs, all products' pictures are saving in products folder, and others are saving in blogs folder.
2) to create many sub folders in products and blogs, each product's pictures are saving in different folder in product by productId, each user's blog pictures are saving in user's own folder by userId.
3) to create folders for each user, and one user's pictures, no matter product or blog pictures, are saving in one folder named by userId.
4) to create folders each day, say, all today's pictures are saving in 20090911 folder, and new day's pictures saving in new folder.
Which way is best? is there any different for those 4 methods?
And for products pictures, I would like to resi ...