you can also donate excess cash to UNICEF
www.unicefusa.org/campaigns/changeforgood
this for the currencies still circulating
and
www.unicef.at/unternehmen.html via Euromoney24 for
all the pre-EURO currencies you might have like Dutch guilders, German mark, Slovenian tolar, Austrian schilling, Portugese escudo, Spanish peseta, Belgian and Luxembourg franc, Maltese Lira, Irish pund, Koruna of Estonia and Slovakia - that migth be a nice way of using them for poor children.