It's a nice 5-AA battery holder, with 5" leads and a 2.1mm DC barrel plug.
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.
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.
This battery holder uses 3 AA cells to power your electronics, robotic or embedded project. You can do without, but MAN, when you need to hold 3AA cells, you'll need it!