So what about batteries?

Well, let's not waste any time discussing the relative merits of the many different battery technologies available and just cut to the chase and state from the outset that we are only concerned with Lithium polymer batteries for our purposes. 

So here is a concise guide to Lithium Polymer Batteries with some other useful links thrown in for good measure.

Yes, we have all grown very used to just throwing batteries around and not worrying about the damage because they are after all inert, harmless items - this drives the current levels of complacency I witness from users.  Sure, with NiMH, NiCad there is relatively little danger, but now enter the world of high discharge high energy Lithium technology and things get a whole lot more interesting.
Lithium cell technology, both lithium polymer (Li-poly or LiPo) and lithium ion (Li-ion), is quite different from the more commonly used NiCd and NiMH. There are many things to consider before using lithium cells for power. But none is more important than safety. While all cells must be treated with respect due to the energy they contain when fully charged, lithium cells have the highest energy density. They also have some unique qualities that require special safety considerations and it's important to understand the necessary safety considerations.
Charging – Safety   -   IMPORTANT  -
If you are new to flying YOU NEED TO LEARN ABOUT LITHIUM POLYMER TECHNOLOGY. Read on to find out why.
Lithium cells must be charged differently to NiCad or NiMH. They require a special charger specifically designed to charge lithium cells. If you do not own a LiPo charger then look here.  There are many to choose from but this one is a great starter.  In general, any charger that can charge Lithium Ion can charge Lithium Polymer assuming thatthe cell count is correct.

You must NEVER charge lithium cells with a NiCad or NiMH only battery charger.

This is dangerous. Charging cells is the most hazardous part of using lithium batteries.  Maximum care must be taken when charging them. It is important to set your charger to the correct voltage or cell count. Failure to do this can cause the battery to spew violent flames.

Many fires have been directly caused by lithium batteries.

When charging lithium batteries    -  PAY ATTENTION TO WHAT YOU ARE DOING -

Some very useful guidelines for charging & using LiPos.
1. Use only a charger approved for Lithium batteries.
The charger may be designed for Li-Ion or Li-Poly. Both battery types are charged in exactly the same way.
2.Make certain that the correct cell count is set on your charger.
If you don't know how to do that, get a charger that can detect the cell count.  (Read the section on understanding Lithium Polymers)
3. Before you charge a Lithium pack, it helps to check the voltage of each cell individually.
You can do this by getting a balancer & cell checker.  It pays to check the individual cells about every tenth cycle.  Why is this important? - An unbalanced pack can explode while charging even if the correct cell count is chosen. If the cells are not within
0.1 volts of each other then charge each cell individually to 4.2 volts so that they are all equal.  If after every discharge the pack is unbalanced you have a faulty cell and that pack must be replaced.
4. NEVER charge the batteries unattended.
This is the number one reason for houses and cars being burned to a crisp by lithium fires.
5. Use a safe (prepared) surface to charge your batteries.
Do this so that if they burst into flames no damage will occur. Vented fire safes, pyrex dishes with sand in the bottom, LiPo charge bags, are all good options.
6. DO NOT CHARGE THE PACK AT MORE THAN 1C.( ie. minimum charge time is 1 hour) I have had the unwelcome experience of a fire in my home because of violating this rule.
7. If a cell balloons while charging DO NOT puncture the cell while it is still hot.
Put the cell/pack in salt water (ratio 1:3) and wait until the cell has cooled.
Once it is cool:
a) Take out of the salt water
b) Gently puncture the pack's outer casing (keep well away from the pack)
c) Put it back in the salt water

After this the cell is safe to throw in the garbage.

8. VERY IMPORTANT: If you have a crash - your Lithium cells may be damaged.
There could a short inside the cell or the package could have suffered damage.  If you have a crash  carefully remove the battery pack and watch it carefully for at least the next 20 min.  Many fires have been caused by damaged cells being thrown in the car and then the cells ignite later and burn the car completely.  Nice hey...
9. Charge your batteries in an open ventilated area.
If a battery does rupture or explode hazardous fumes and material will spew from the battery.
10. Keep a bucket of sand nearby when you are flying or charging batteries.
I actually keep a fire extinguisher.
11. Do not commit the error of complacency, these batteries are dangerous!
Do not think that “it won't happen to me” because it will happen to you and you'll be trying to rescue your kids from your burning house or car.