"on the fly" means you can simply upload your images and with a bit of coding, these can be automatically resized to thumbnails and displayed, from the serverside... this can be done in .asp .php flash xml etc etc .. but as you are not familiar with these, I was suggesting purchasing a product that will do that for you..
It maybe worthwhile and save you a good deal of time in the end, if you are becoming over run..
I don't know how much work is involved for you or what you need exactly? but ..
you could have your users upload the images themselves, attaching notes / comments, links etc .. and the thumbnails can be displayed with out you having to do anything..
again there are a number of products that can do this..
imagevue being one ... there is also this dreamweaver extension.. [interaktonline.com...]
and a number of gallery products ... like 'simplephotos' [ppleyard.org.uk...]
or 'Archetype' [thinkist.net...]
in fact have a search and you will find many...
So if you want to do it yourself or use a ready made product, either way you've just got to decide what is best for you, first.. IMO
ps: burn Front Page ;)