Programs written in JavaScript or using older versions of Flash will run on many computers including the Elonex ONE and Elonex ONEt.
A useful source of JavaScript programs is as Firefox Addons: https://addons.mozilla.org/en-US/firefox
You should take care to choose add-ons that suit the version 2.0.0.0 Bon Echo or Saramao Internet Browsers on the Elonex ONEt or ONE respectively.
I particularly like SQLite Manager https://addons.mozilla.org/en-US/firefox/addon/5817 which is both a good early introduction to databases and an easy way to construct your own simple record keeping system, your personal music catalogue, contacts list or whatever.
Adblock Plus https://addons.mozilla.org/en-US/firefox/addon/1865 is good at removing adverts from Internet pages - there are also plenty of games and simple programs to help make more use of your Elonex.
There are thousands of "Flash Games" on the Internet - try http://www.google.co.uk/search?q=flash+games as a starting point - but beware that many expect your screen to be bigger and your processor to be faster than available on the ONE or ONEt. You may be able to play the game "live" on the Internet on your browser, but you can also save the game by right clicking on the space where it plays in the Internet page and saving the file as a ".swf" file type in your "My Games" folder - then when you launch the Flash Player on your ONEt you can choose File - Open to start any of the games in the My Games folder.
Sites with specialist Elonex ONEt software
http://www.littlelinuxlaptop.com/software.htm has a number of useful games and programs that have generally been tested and are known to work on the Elonex ONEt(+), the Dutch Trendtac 700 EPC and the Maplin CnM Minibook.
http://194.150.201.35/cnmlifestyle/downloads.htm is primarily aimed at the CnM Minibook - but most of the software also works on the ONEt - this includes more games, a spellchecker for the Abiword Wordprocessor and some printer and 3G drivers.
http://freespace.virgin.net/hugh.satow/gtk/ has some Card Games and some Puzzles and a quick note taking program - I particularly like the puzzles.
Each of these additional programs use up one of the icon spaces on the Elonex ONEt desktop - you have 5 screens of 15 icons, 75 in total - and some of the icons only want to display in certain places, which can mean that sometimes you add a program and don't see an icon because it's hidden by one for another program. To solve this you need to edit the relevant .desktop file. The simplest way to do this is to use the "Nedit" program downloaded from http://www.littlelinuxlaptop.com/software.htm - launch the program, then select file open and type in the full path name of the file you want to edit - you discover the pathname by using the Bon Echo Internet Browser - type the address file:///share/applications into the Browser address bar (and, yes, you do need three "slashes" together - the pathname you want is: /share/applications/programname.desktop - replace programname by the actual name used for the file, when you edit the file the number on the line that starts Categories= determines which screen the icon appears on (numbered from 1 to 5) and the number on the line that starts ItemIndex= determines the position on the screen (numbered from 0 to 14) - a number of -1 means "place at the end" a # symbol at the beginning of a line makes it a comment so it's ignored - leaving out or commenting out the ItemIndex= line let's the Elonex place the icon at the earliest available position - if an icon cannot be placed at the requested position it will be placed at the next available later position (but never at an earlier position) - the actual places are determined by the order in which the files are read when the computer starts - so you won't see your changes until you restart the computer.
You can now understand why I quite like Firefox Addons and Flash Games (they don't use up any of your icons) and Games and Puzzles where one icon launches a program giving you access to many games or puzzles (they give you a lot of value for each icon used).