<p>Cressida, are you looking for a model kit for high school classes? Depending on your level of familiarity with molecular modeling, here are several computer programs you can utilize for this purpose without paying huge $$:</p>
<ol>
<li><p>Check ChemDraw by Cambridgesoft - it is a chemistry drawing program and an add-on to it allows 3-D renedering of organic molecules, both space-filled and ball-and-stick that makes molecules look like those plastic kits. There should be a free trial download available and academic pricing, too.</p></li>
<li><p>Ages ago, when I was in grad school, I bought one of the first versions of HyperChem (may be even the first version) - a neat 3-D modeling software for Windows-based PC (in those days, most programs for modeling run on very expensive Silicon Graphics computers).</p></li>
</ol>
<p>[HyperChem</a> > Home ( DNN 4.3.5 )](<a href=“http://www.hyper.com/]HyperChem”>http://www.hyper.com/)</p>
<p>HyperChem is still around, and now it can be run on a Mac, too. It might be a bit too complex for what you are trying to do.</p>
<ol>
<li><p>I had some good experience with ACD Labs’ software in the past, too. I have not used it in years, but it might fit the bill perfectly for your use since it is supposed to be very simple to use.</p></li>
<li><p>The plastic modeling kits can be obtained from Aldrich or any other scientific supplier:</p></li>
</ol>
<p>[Molecular</a> Models](<a href=“http://www.sigmaaldrich.com/catalog/search/TablePage/18291286]Molecular”>http://www.sigmaaldrich.com/catalog/search/TablePage/18291286)</p>
<p>[MolyMod</a> molecular models](<a href=“http://www.sigmaaldrich.com/Area_of_Interest/Equipment_Supplies__Books/MolyMod.html]MolyMod”>http://www.sigmaaldrich.com/Area_of_Interest/Equipment_Supplies__Books/MolyMod.html)</p>
<p>Frankly, I have not touched a plastic model in ages, so I can not be of much help here.</p>