sesecuring access to workgroup for notebooks

Hi all. I need some hints and opinions in order to perform risk assesment and 
... for the following situation.

in a win based network, some users (mostly interns)
access using their own notebooks. they have to get/send corporate email, access 
to common, server-based document folders, access to printing resources. At the 
present time 
all network is organized in a workgroup.
In the future i will implement domain access and terminal services, but in the 
meanwhile i need to get the best from this config. Would please someone give me 
some hints?

thanks