What is commonly done is users buy a file server, say OSX server from apple, to solve this type of problem. However if your not running a server anywhere then you are correct that you have to do the following:
1. Turn on file sharing under system preferences.
2. Mount each drive that you need access to under Network, Go, finder menu.
Leopard in a few days may offer more ways, but file sharing is generally consider a security risk and thus not made extremely easy or optimized - Unless you use a file server.