ok, I put the function in the right place and I'm calling it in the .ss page, but I'm getting this error:

Error
The website server has not been able to respond to your request.

I'll keep checking things, just to make sure I didn't leave something out.

No idea. That's almost the exact code I have in use right now.

Cheers
Aaron

hmmm, what did you put in your .ss page?

moloko_man, append ?isDev=1 to you URL to get the error message.

wow, lots of errors :( still a noob at this, but trying to figure it out.
here is what I get:

FATAL ERROR: Bad class to singleton() - Products
At line 85 in /Applications/MAMP/htdocs/biomicro.com/sapphire/core/Core.php

user_error(Bad class to singleton() - Products,256)
line 85 of Core.php

singleton(Products)
line 1572 of DataObject.php

DataObject::get_one(Products,,,RAND())
line 18 of HomePage.php

HomePage_Controller->getRandomObject()

call_user_func_array(Array,Array)
line 404 of ViewableData.php

ViewableData->XML_val(getRandomObject,,1)
line 12 of .cache.Applications.MAMP.htdocs.biomicro.com.tutorial.templates.Layout.HomePage.ss

include(/private/var/folders/wO/wOacFITKFUaUHT-w02HAXk+++TI/-Tmp-/silverstripe-cache-Applications-MAMP-htdocs-biomicro.com/.cache.Applications.MAMP.htdocs.biomicro.com.tutorial.templates.Layout.HomePage.ss)
line 197 of SSViewer.php

SSViewer->process(HomePage_Controller)
line 189 of SSViewer.php

SSViewer->process(HomePage_Controller)
line 296 of Controller.php

Controller->defaultAction(index,Array)
line 267 of Controller.php

Controller->run(Array)
line 22 of ModelAsController.php

ModelAsController->run(Array)
line 27 of RootURLController.php

RootURLController->run(Array)
line 104 of Director.php

Director::direct(/)
line 158 of main.php

This is because you're trying to get a singleton of products instead of Product. Use:

function getRandomObject() { 
      return DataObject::get_one('Product', null, false, 'RAND()'); 
   } 

instead.

even with that change I still get a whole list of errors. in the get_one() function, what is the first item referring to? i.e. get_one('Product', null, false, 'RAND()'); 'Product' should be the section?

could it be that I have two sub levels to the Product page? I have the product page, then a page for each product and then pages for specs, publications, etc. should I just be sticking to one sub level?

Product is the name of the class you're trying to get one of. Do you have a Product class?