I've had 1 Euro change sellotaped to a package underneath the stamp before. I thought it was quite cool, as some people wouldn't have bothered.
As for the Euros, well keep 'em.
Heh, I guess its not so easy for you, being the other side of the atlantic. But I came back from Finland a few years ago with left over Euros, and spent them in France when I was next there. Then I came back from France with some left over Euros, and spent them when I was in Ireland earlier this year. Of course, I came back from Ireland with left over Euros too. I conveniently went to Germany two weeks ago...
I accept Euros and Dollars as cash payments when I sell stuff on ebay, as I know I'll use them sooner or later.
Perhaps you ought to use the 3 Euro as an excude to visit Europe, eh? ;-)