However, since I'm going to a new method of framing, I'd like thoughts on what
you have used as workbench/shelving materials. The benches will be about 2'
wide and 6' long. Yes, I know, solid moulded Teflon would be best, but quick
and cheap is high on the list of attributes I'm looking for.

Restaurant supply houses that specialize in used equipment will have
stainless steel tables. Size / price / condition will vary. Might be
able to find a butcher's table. I suspect that it's a sheet of
teflon-like stuff (those white plastic cutting boards) laid over SS.

Plexiglas / Lexan? You could stiffen it up with bracing on the
underside.

Foam board used for insulating houses and some a/c designs? You can
get it thick for stiffness, though it won't handle beating on. It'll
take pins well if you're building balsa models or laying out wiring
harnesses. Just don't try to solder on it. ;-^

Corian / synthetic stone counters. Not cheap, unless you can find one
salvaged or scrap. Some towns have architectural recycling centers
where you can get pre-owned building materials cheap. (Might even
find some old luan doors.) They might have a counter top or two;
likewise the manufacuter or an installer might have a damaged or
customer-rejected one they'd unload at cost.

Why do you want a non-wood top, anyway?