The Smartphone Experts network is a network of web sites about each of the different types of smart phones. The sites have news articles, reviews, tips, discussions, and more about each one.
If you have a smartphone, you should check out the site for your phone and subscribe to the feeds. The tips, tricks, and info that I have learned is great. You can also find solutions to issues or problems you may have.
Android Central - for Google Android phones, like the T-Mobile G1, Droid, HTC and more.
Crackberry.com - for Blackberry phones
Nokia Experts - for Nokia phones
The iPhone Blog - for Apple iPhones
Precentral - for the Palm Pre, Pre+, Pixi and Pixi+
Treocentral - for Palm Treo's and Centro's
WM Experts - for phones running Windows Mobile, like the Palm Treo Pro and HTC phones.
These sites are great resources for smartphone owners.