One of the issues we all encounter is the power sources that make our digital gear alive. There are many types of sources and many variables that affect their work. In the article posted at SmartShooter.com I found about a new rechargable batteries that can could solve most of your problems and save you a great deal of money. I have to note that to read this article you have to regitster on the website.
These batteries could replace your AA alcaline batteries, but it may not be the solution for some of other issues. Such as power for your external flash, your professional camera or laptop on the go. But there is another manufacturer, which produces great (but somewhat expensive) solution to these kind of issues. And the name of the manufacturer Digital Camera Battery. For my 550EX flash I purchased 40W battery, pro-cable and the case with the belt clip. The cable allows the flash to burst almost every second - recharge time is a bit more than one second.
To learn more about various types of batteries - read the article written by Ken Rockwell.
You may want to look as well at one of the previous posts here - Initial conditioning for NiMH battery (Thursday, October 14, 2004)