Read the thread started by C130Driver about altering a foam humidification device and the subsequent posts about Boveda and recharging them.
I do this frequently - my local B&M saves the Bovedas that come in the boxes they buy and I occasionally grab a handful when in the shop.
I found these divided Rubbermaid "Take-Alongs" for about $2.50 for a three pack at a local dollar store (Walmart, grocery stores carry them too) that are prefect for recharging. Just add a little distilled water in the smaller reservoir, put the Bovedas in the other side, put the lid on it and... voila!
I maintain several to separate the different humidity levels (69, 72, etc.). Trust me, you have to do this!
Once recharged, just put them in a zip-lock bag. Or, leave alone - they'll reach a saturation point and stop taking more moisture.