The ReVIVE DUAL-ion+ dual battery charger from around $20 can handle both Canon and Nikon DSLR batteries as well as other small cameras and non brand batteries via interchangeable adapter plates.
Dual Battery Charger allows you to charge two batteries at the same time quickly and efficiently, Status LED Display for Real Time Charging Progress, Auto-cutoff enables trickle-charging when full, Utilizes MPC Technology for Fast and Smart Charging. AC, DC world-ready 100-240 volt, Charges either 1 or 2 Batteries! Additional interchangeable charging plates for other battery types are also available.
Thanks to AccessoryPower for the video:
Do a Google search and order ReVIVE DUAL-ion+ dual battery from your favourite online store.