On the 1st of April there will be new regulations for the transport by air of Li-Ion batteries.
http://www.iata.org/whatwedo/cargo/dgr/Pages/lithium-batteries.aspxDetails for passengers can be found here
http://www.iata.org/whatwedo/cargo/dgr/Pages/dgr-guidance.aspxIn short:
- Everything below 100 Wh can be brought along without limitation in numbers but spares must be transported in the carry-on bagage (or pockets)
- Between 100 Wh and 160 Wh approval of the operator is needed and spares are limited to two pieces
As a reference the mighty D3 batteries were roughly 27 Wh (2500mAh x 10.8V) so its safe to assume that the batteries for the average camera is well below the 100 Wh limit.
Laptops might be a little more tricky, the smaller models should be well within the 100 Wh limit but bigger laptops like the latest MacBook Pro Retina 15" barely makes the 100 Wh limit with it's built-in 99,5 Wh Li-Ion battery.
Watts-hour (Wh) is Amp-hour (Ah) times Voltage (V), both are usually mentioned on the device or battery but these are the commonly used voltages (some are labeled slightly lower):
- 3.7V: The flat batteries used in pocket cameras, smart phones, laptops, 18650, etc
- 7.4V: The batteries used in most DSLR and mirrorless cameras (contain two li-ion cells)
- 10.8V: Used in the professional cameras like the D3, D4 and D5 (contain three li-ion cells)
The official IATA table with the details