Yard/estate sales is another source.
I subscribed with Estatesales.net & every week I get a list of sales (usually about 10 all over LA county). Most are too far away or don't have any pics of what they have.. & they tend to ignore what's in the garage.

Be careful tho.. next thing ya know you'l have a dozen vices in the shop. I was welding up a Kaw Z1R gastank in my garage today when a friend dropped by & after he'd been here a few minutes he realised there were vises all over the garage......... & then promptly offered to bring me (for free) "2 or 3 large old US made vises that are cluttering up the barn". No idea what he has, but from the description one of them sounds like a blacksmith vise.. & I don't have one of those yet

What the heck, it's a cheap hobby & it ain't like anyone is going to steal something weighing 80lb & run off down the street with it...
Have a look on Craigslist also. I spotted this yesterday:
http://losangeles.craigslist.org/sfv/tl ... 07504.html Yeah, thats the silver one I have now, missed the blue one..

Anything with 6in or bigger jaws fetches BIG $$$
Some people are just delusional:
http://orangecounty.craigslist.org/tls/1959663673.htmlI have 2 of those, the green one cost me $50, the other is the one that showed up today for $65.... NOT $900 LOL!