3
Go to System Admin->Blocks
Here you can create what ever blocks you wish, set their weight (order) and location to the left, right, center-left, center-center, or center-right.
Once created, you will have to go to System Admin->Groups and set who will be allowed to see what block you create. For instance, you may want to create a block welcome users to your site in general and set that for anon users only. When a registered user logs in you can have a new block showing other things, etc.
A search of "custom blocks" may yield more tips and tricks then this small reply.
Good Luck