From Ars Technica, a good article regarding modding/hacking the Asus Eee PC. Some sample tips -

Virtual desktops

The Eee's small screen makes it difficult to see more than a few things at once, and switching between windows quickly becomes frustrating. Support for virtual desktops is one of the Eee basic model's coolest undocumented features. Out of the box, basic mode has four separate workspaces that you can switch between by holding Ctrl and Alt while pressing the left and right arrow keys. If you hold the shift key too, you can move the active window with you to a different workspace.

The Eee basic mode environment doesn't provide a graphical display of your workspaces, so it can be pretty easy to forget where you have your windows. To get a visual workspace display, you can run the kpager utility from the command line.

GVim and KPager running on the Eee.

You can also add a workspace switcher to the basic mode panel by creating an IceWM preferences file at ~/.icewm/preferences and adding the following lines:

TaskBarShowWorkspaces=1
WorkspaceNames=" 1 ", " 2 ", " 3 ", "

Installing extra IceWM themes

Alternate IceWM window themes can be downloaded from Freshmeat and installed into /usr/share/icewm/themes. Then, to switch between themes, add a theme chooser submenu to the IceWM start menu by adding the following line to ~/.icewm/preferences:

ShowThemesMenu=1

Fixing the fonts

By default, the Eee uses size 10 fonts in most of the programs, which may or may not to be your liking. Unfortunately, there is no central location where you can go to change all the font sizes. You have to configure the font sizes individually for Firefox, GTK, and KDE. To change the default KDE font size, launch the kcontrol utility from the command line, navigate to the Display/Themes/Fonts page, and change the font sizes.

The Eee doesn't come with the GNOME font configuration utility, so you will have to create a custom ~/.gtkrc file to set up a default GTK font. In my .gtkrc file, I also force GTK to omit labels from toolbar buttons in order to save more screen space. This is my ~/.gtkrc file on the Eee:

gtk-font-name = "Sans 8"
gtk-toolbar-style = GTK_TOOLBAR_ICONS

To change the default interface font size in Firefox, you will have to modify the chrome css file, which is located at ~/.mozilla/firefox/*default/chrome/userChrome.css. This is what I put in my userChrome.css file to make the interface use font size 8:

* {
font-family: sans-serif !important;
font-size: 8pt !important;
}

You could probably also customize Thunderbird's default font size with a userChrome.css modification.

You can read the complete article which lists a lot of other tips and info here.