I throw all my change into a couple of Ragu jars, sorted by type. Pennies in one jar, dimes in another, and so on. To get a rough estimate of how much moolah I had, I figured I could weigh the jars and convert the weight directly into dollars. Haven’t had much luck finding dollars per pound figures for change though. Anyone have a clue?
Check out this interesting article from Fortune. It says a quarter is 5.7 grams and a penny is 2.5 grams. Don’t know about the other coins, though.
As I recall, the “silver” coins (quarters and dimes) have the same “value density”, as do the “base” coins (nickle and penny). In other words, a dollar’s worth of quarters would weigh the same as a dollar’s worth of dimes, and a dollar in nickles would weigh the same as a dollar in pennies. I think that the Kennedy half-dollars might have had the same “density” as the quarter, hence the silly-looking size, but I’m not certain about that.
A couple of decades ago, the composition (and hence weight) of the penny was changed; I’m not sure if this rule held for the new or old system. Since you’ve probably got a good number of old pennies in there, though, you wouldn’t be able to expect accuracy, anyway.
Here’s what the US Mint has to say:
Penny: 2.5 grams
Nickel: 5.0 grams
Dime: 2.268 grams
Quarter: 5.670 grams (this may have changed with the state quarters)
Half Dollar: 11.340 grams
Susan B. Anthonay Dollar: 8.1 grams
Sacagawea Dollar: 8.1 grams
Using that as a base, a pound of quarters should be about $20.00, a pound of dimes is about $20.00, a pound of nickels is about $4.55, and a pound of pennies would be about $1.81.
Forgot to add that Chronos was on to something:
A pound of dimes, quarters, and even half dollars all have the same value.
As for the pennies and nickels, well, he’s was at least half right. 
Well, that’s pretty interesting. We didn’t know the numbers, but this issue comes up in D&D games, because under the older rules, ten gold coins weighed a pound). Obviously, that’s silly. But we’ve been using the rate of 50 coins per pound for years, and this data seems to validate it, since presumably a gold coin would weigh around as much as a dollar, and at this rate it takes 65 quarters to make a pound, or 46 Sacky-G’s.