Windows Network Access for Guest Type Users?

Hi,

I have a network with a SBS2003 Server. My boss wants me to allow any of our clients to plug their laptops into the network and have access when they are here for meetings, but wouldn't they need to join the domain and log in so they can get an IP Address? I don't have all that much in knowledge of windows server, but I am the resident expert by default because I am the web developer.  It does seem like a simple thing that businesses would need. Allow people to easily yet securely access their network to copy files or access the internet, especially if they have physical access to a network drop, but there always seems to be a catch. Any help on how to do this is greatly appreciated.

We also have an internal 128bit secured wireless that he thinks should work this way too. But it is a netgear router and seems to only support 1 key so if we give the key out people will be able to access our network whenever, or we will have to change the key after each Guest use, which will make all of our employees who are using the wireless mad all the time.

Thanks!