My current preferred Windows Mobile phone is my T-Mobile Shadow (that will soon be replaced by a U.S. model HTC Touch Dual as soon as trhey are available). The one issue I have with my Shadow is the rather short battery life. There looks to now be a solution that solves this issue for less than US$60.
The folks at AllShadow.com just posted a review on the new ElectraSpan extended battery that is now available from BoxWave for US$59.95. The current battery has a 900 mAh battery capacity and this new one gives you a whopping 2200 mAh. The test results were quite impressive and showed 2.25 times more runtime with this battery. Now the battery is larger so a new back is included for your Shadow. While the back does stick out a bit, it looks to be in the area where it should fit well in your hand. I almost placed my order last night, but with my planned future purchases I will hold off for now. The regular price is shown as US$89.95 so if you like your Shadow and want more battery life you may want to take advantage of this current offer.