i've been going thru these 10 crates. I googled a few old/interesting ones to check on value. Not worth much at all. As rippy said very few above face value. I'll be lucky to average $1/stamp, though the sheer volume of stamps here probably makes it worth selling.
I did find a handful around $20/stamp, but very few.
More than monetary value, though, as quadibloc said, it does have some genuine educational value. I wound up wiki-ing a bunch of historical names and events from different countries that i hadnt heard of before, that had been commemorated on stamps. Learned something.
Also some of them are truly historically fascinating. Dad had a huge collection of stamps from colonial india, some of them around 1820, 1840 etc. Thats fairly old, real antiques, full of history, and is a great way to learn about that era.
Sadly even those arent worth much on the open market, as far as I can tell. But very historically fascinating.