As enamel stated, the occasional dealer will buy them by the pound. This is fine for non-rare, obsolete coinage but you can likely do better for the spendable coins.
This place buys (non-obsolete I assume) coins from certain countries. I've never personally dealt with them, nor know anyone who has, so I can't say if/how and how well/quickly they pay, etc.
Ebay is another option. The few lots I've noticed of spendable, non-obsolete foreign coinage seems to sell close to face value. Of course there's shipping and the ~13% ebay/paypal fees.