Occasionally, when I am in a hotel, the IP address (or subsequent routing) conflicts with our own internal IP addresses or routing.  For example, I was in a hotel in Dallas recently and I got a 10.1.0.x address from their DHCP server.  Since the hotel was using the same IP addressing scheme as our office network, I was unable to VPN into our office. [more]

This is when it comes in handy to have a portable router.  [more] I personnaly carry with me a Linksys WTR54GS:

This is a wireless router but can be used as a wired router.  If I plug the router into the hotel's network then plug into the other side of the router, I get a 192.168.x.x address from the router and then I can VPN through the router to our internal network.

 The router I use also is handy since it's a wireless router with one Internet and one Ethernet RJ45 connection.  If the hotel is wireless only, I could configure the router to connect to the hotel’s wireless and then I could plug into the internal port to get behind the router.