When totally discharged (ie, to near zero) they should be fine (should be able to go to standard battery disposal). Got any meaty resistors around?
Ok, I'll eventually dispose them. But no, no resistors left around, sorry.
aka. low-wattage incandescent bulbs?
Plenty of those around, actually. How low?
Even if they're completely flat, don't try to break them open or short them :P
Ok

I'll actually make sure they're well protected, if there's still some chance of fire or explosion. The worst thing is to keep them there and forget they even exist.