There is a new download available on the ArcPad Resources site, and it's pretty cool!
The applet allows you to download the tiles of a ArcGIS Server cached map service to your computer/device so you can still have beautiful cartographic basemaps when working without a network connection. This means you can download the area or interest and store it before you even go out into the field. You can also copy it across all your devices before going out into the field.
The tool will allow you to download any number of services that are in your ArcPad map but if you try to download lots of data, it may take some time. So I suggest NOT trying to download the entire planet at level 20!