Bob in Texas asks "With SQL Denali supporting network shares to store databases on remote machines can older Windows 2003 servers be used as the remote file server?"
The answer to this is shockingly enough "it depends". Technically yes a Windows 2003 Server can be the file server hosting a remote SQL Server database. However it would be better to use a Windows Server 2008 R2 server instead. The reason for this is that Windows Server 2008 R2 introduced SMB 2.0 which is much more optimized than the SMB 1.0 protocol which Windows 2003 Server supports.
SMB is the network protocol that Windows servers and workstations use to talk to each over and do file share transfers. The SMB 1.0 protocol is a very chatty protocol which requires a lot of overhead which means that there is much less room in the network cable for data traffic. One of the big improvements, probably the biggest and most important, was the reduction of network chatter with SMB 2.0.
SMB 2.0 is fully backward compatible with SMB 1.0 which allows newer operating systems such as Windows Server 2008 to communicate with older platforms like Windows 2000 and Windows 2003.
For smaller lower load databases it would probably be OK to host them on older OS file servers like Windows 2003 Server, however for larger higher load databases you will really want to look at upgrading the file servers to Windows Server 2008 R2 (or Windows 8 server when that becomes available). You may also want to look at NAS devices which support SMB 2.0, but make sure that they support SMB 2.0 before putting databases on them.
As we get closer to the release of SQL Server "Denali" we will begin to see more and more devices which claim to support hosting remote databases. Only time and testing will tell if these devices will be good at supporting remotely hosted databases.