I am not a computer security expert, but I think that security associated with mobile devices requires specific attention. Please read the Security-HOWTO by Kevin Fenzi and Dave Wreski for more information. I just collected some information below. Note, these means are just small steps to additional security, though I recommend that you use them.
Please read also the Linux Administrator's Security Guide (LASG) - FAQ by Kurt Seifried.
Antivirus policy: I have seen an antivir RPM somewhere. Check the BIOS for an option to disable writing at the boot sector.
Laptop as a security risk itself: Since a laptop can easily be used to intrude a network, it seems a good policy to ask the system administrator for permission before connecting a laptop to a network.
Secure Protocol: When connecting to a remote server always use a secure protocol (for instance ssh) or tunneling tunnelv , pptp and APOP for POP accounts.