Well, you can turn a pile of coins into more useful (minimized number of units; notes, etc.) money, but they take a cut (8.9%, I think). There is a way to get 100% of your money, however: Turn it into a gift certificate for Amazon.com or Starbucks or several other options and they take 0%. That deal has been on-going for a couple of years now, I think. It's standard.
Right now, however (Amazon e-mailed me this morning), if you turn at least $30 of coins into an Amazon.com gift certificate, you can then mail in the receipt to receive an additional $10 Amazon.com gift certificate by mail.
I happen to have had $41.48, apparently. :) (and now I have that in my Amazon.com account -- the GC code on the receipt can be for any arbitrary amount, which is nice; I heard the modem dialling in the machine so it could acquire a code for a specific value). That, and I'll be receiving another $10. Yay!
Y'know... if you don't have $30 in coins lying around, you could even go to a bank, ask for $30 in quarters, and then go to the Coinstar machine, ... ;)