It has been my experience that a Linux system is much more usable if it’s connected to the Internet, because then the package management system can be used to resolve the dependencies of the programs. From what I’ve seen (and please bear in mind that I’m fairly new to it), in Linux it is much more common to reuse programs / libraries and there is much less reinventing the wheel going on than in the Windows world. I can only theoretize as to what the reason may be for this, but I think that the clear-cut licenses may be the main reason (basically almost everything is under the GPL – meaning that a programmer knows that s/he can reuse all the other pieces of code).

While this makes for a much more pleasurable experience for the developer, it makes the software harder to install, because you have to have all its dependencies (the libraries/programs it relies on) and their dependencies and so on. A package management system makes it seamless if you are connected to the internet.

However if you have no access to the internet, under Ubuntu you can export the download instructions to a file, which you can take to a computer connected to the internet and execute it. If the given computer runs Windows, you can still use this file to download the packages, just get WGET for Windows, rename the file such that its name ends with .bat (for example download.bat) and remove the first line (the one which begins with #!)

An alternative to this is hyperget, a new project which aims to make this process even more simple.