Other than having my laptop with me at all times, I use the following services to get to my most needed things when not at home:

* bookmarks on Delicious
* documents on DropBox
* music on an iPod with me

I'm a computer system administrator and I think before the internet age my job would have been much harder to do, although the general list of the tasks I do would have remained the same.

I work on corporate systems on a day-to-day basis, and use the internet primarily as a tool to find answers to my problems. The big advantage of having internet is that someone out there is bound to have come up against a similar problem and so it cuts down on my troubleshooting time.
Of course, due to the nature of my job I am inevitably doing work directly related to the internet like managing websites, which would not have existed pre-internet.