If you are a Windows Phone developer and want to implement logging in your Windows Phone Apps, below are list of few Logging Framework that you could try.
1. Silverlight and WP7 Exception Handling and Logging building block
An Open source project which can be downloaded from CodePlex lets you handle and log client side exceptions in your Windows Phone projects.
NLog for Windows Phone 7, Advanced .NET Logging supports Windows Phone, Silverlight, .net
3. Crypto Logger For .Net (v2010)
Crypto Logger For .Net is a flexible and high-performance logging framework for your .Net Apps and supports .NET 4.0, Silverlight, Windows Phone
Please feel to include any other Logging frameworks in the comment section if it is missed out in the above list. I will update the list accordingly .