Sometimes you may find that you cannot find a Xandros, Debian, Ubuntu or other .deb package for the software you want to install. This is the case with gpsbabel, for example. Instead, you are offered the opportunity to retrieve a .tar.gz file (e.g. gpsbabel1.3.4.tar.gz). How to install this on your Eee PC?
Firstly, read up on the process of installing software from source in this article at tuxfiles.org.
Next, you will need to install a package of development tools including the gcc compiler. The easiest way to do that is to install the build-essential Debian package.
You can also choose to install the various pieces by hand. In this case, you will need to install the following packages: gcc, autoconf, automake1.7, expat, libc6-dev, libexpat1-dev. I'm sure you'll agree it's easier to follow the first route.
Now grab your desired source package, untar it, and follow the installation process described on tuxfiles.org.