It's a nice 5-AA battery holder, with 5" leads and a 2.1mm DC barrel plug.
This is a coin cell holder for the common CR2032 type battery. The holder has a neat pop-in, pop-out feature that makes changing the battery easy.
Looking for a portable USB device charger, like for an iPod, Zune, or similar portable electronic device? The MintyBoost is a fun kit that lets you recharge on the fly, from a pair of normal AA cells!
This is a 9V battery pack with on/off switch and a 2.1mm barrel plug, you get both parts and will have to solder them together. Use this to battery-power your Arduino (or other electronic projects).
It's a nice quad-AA battery holder, with 6" leads.
A nice 6AA Battery holder in black plastic with wire leads.
Need to add more voltage to your regular 4AA battery pack? Parallax has come up with this ingenious plug in module that adds a 5th module to your AA quad-pack holder.