sesecuring access to workgroup for notebooks

[Davide <ak_71 () libero it>]

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