Depends on the level of curriculum you're trying to create. I could say so much more than the $.02 I should offer .... teaching computer literacy (vs. say, "computer science") can go through many different levels ... typing skills, keyboard familiarity & on up. When I taught 6th graders computer literacy & some computer science I exposed them to a bit of everything
Mavis Beacon (cheap, $5/seat) to learn typing, they enjoyed making weird monsters in the game piece.
Celestia, the astronomy program, to learn keyboard navigation shortcuts & make astronomical animations.
Gimp, to make simple tessellations that they printed out & took home.
Open Office, to make presentations in Impress (I'd suggest getting the Novell GoOo distribution of OOo).
And BugBrain,
to teach them simple programming via a neural networking curriculum:
http://www.biologic.com.au/bugbrain/(this, BTW, is one of the coolest things I've ever seen when it comes to teaching logic ....)
For fun in teaching programming I should also mention Alice & Gary's Mod ....
I taught the older kids some heads-down programming using Python, the Idle IDE & the VPython lib: http://vpython.org/vpythonprog.htmI've done enough programming in Open Office Visual Basic to say that although the memory leaks are tolerable for small projects the Calc debugger is pure heck. I've becoming reasonably familiar with Kompozer to say it's ready enough to teach HTML5, CSS, but with the failure of the XHTML 2 project careful to not be led into a dead end. I'd also look into other
WYSIWYG HTML development tools ... unless you are loathe to let Microsoft into your curricula, M$ has its free Visual Studio Express series including Visual Web Expressions... I'd want to evaluate its HTML for validity & neatness.
If I had to chose on how to teach beginning structured programming to older students I'd look at Microsoft's free VB.NET Studio Express ( (C#, VB or IronPython), Lazarus (Delphi-like OO Pascal) or maybe the xBase revival XHarbour.
see also: http://www.codeplex.com/IronPythonStudio
FWIW there's an interesting project, "XML VM", that's crosscompiling Java to _javascript_, Objective C (iPhone), etc.
/lee