So... good news and not so good news.
The good news, is that with the Internet, you can quickly identify whether or not any of your stamps are valuable. Here's a basic site that has a great list of things to compare what you have with valuable stamps:
http://www.sandafayre.com/rarestamps/rareunitedstatesstamps.html
Note: I have not checked any of your stamps against the list.
The not so good news is that stamp collecting is really falling out of fashion. There was a whole generation of people who collected avidly, and the next generation does not. This has resulted in a flood of stamps on the market not really "wanted" by anyone. I personally got into stamp collecting with my grandfather, who started me up, and I collected commemorative stamps for years convinced that 20 -30 years later, they'd be worth so much more than what I paid. As a 12-16 year old, I invested hundreds of dollars into just the rate plate blocks, and regularly purchased sets from the Post Office. 30 years later, the stamps are still worth face-value. And if I were to try to sell them as a block, I'd probably only be able to get LESS than face-value. In short, I'm better off USING them, than selling them (unused stamps are still worth what's printed on them).
In fact, it's not uncommon to see people purchase "collections" for pennies on the dollar, just to use the stamps for their business (I regularly get numismatic periodicals with stamps from the 1980s on them).
In fact, the value has dropped so much, that event the "rare" stamps are a fraction of their worth 30 years ago (with a notable few specifics, like the inverted Jenny). The Graf Zepplin was considered a "holy grail" of stamps for enthusiasts. They could be had for $10,000 or more when I was a kid, and my grandfather was convinced they'd be worth $100K or more in 25 years... Here it is 30 years later, and you can pick them up for less than $1,000. There's just no interest in them.
Too many collections "inherited" that have flooded the market, and not enough collectors.
Contrasted to US coinage, and the difference is marked. I wish I'd invested in Large Cents, when I was a kid, or even Morgan Dollars (which could be had for about $1.80 to $4.00).
Skippy