Here comes a short list of managed classes/libraries developed by the community members , which may speed up your regular dev activities.
Note that some of them are not complete solutions, but they may give you a good idea how to acomplish tasks considered as hard for the regular managed dev.
1. Managed Today Item
by Christopher Fairbairn
http://www.christec.co.nz/blog/archives/281
2. Managed Notification With Soft Keys
by Christopher Fairbairn
http://www.christec.co.nz/blog/archives/150
3. Improved OpenFileDialog
by Christopher Fairbairn
http://www.christec.co.nz/blog/archives/286
4. Managed Services
by Peter Nowak
Actually it isn't possible to create Windows Services for Windows Mobile and Windows Embedded CE in managed code.
Pavel Bánský's shows in his blog post, how Services in Windows Mobile in managed code can be created...
http://blogs.compactframework.de/Peter.Nowak/2008/05/31/Dienste+Mit+Dem+NET+Compact+Framework+Erstellen+Creating+Services+With+The+NET+Compact+Framework.aspx
5. DynamicDNS Library
by Peter Nowak
Library to update dynamic DNS providers like DynDNS.org , NoIP.com and others. Usefull in some "push" scenarios
http://blogs.compactframework.de/Peter.Nowak/2007/11/29/nahtlosmobilde+DynamicDNS+Library+10+Released.aspx
6. PowerShell Windows Mobile Provider
by Oisin Greham
Explore and manipulate your mobile device with Windows PowerShell. Supports PocketPC and SmartPhone devices; WM2002, 2003, 2003SE, 5, 6 and 6.1...
http://www.nivot.org/CategoryView,category,WindowsMobile.aspx
7. AlphaMobileControls
AlphaMobileControls is a .NET Compact Framework 2.0 API offering WinForm Controls for Windows Mobile 5 or 6 able to handle images with alpha channel and alpha blending.
http://www.codeplex.com/alphamobilecontrols
8. P/Invoke Library
by Warren Tang
http://www.cnblogs.com/WarrenTang/archive/2008/08/28/1278853.html
Projects from OpenNETCF
9. Smart Device Framework 2.2 (Community Edition)
Compact Framework developers know that they have a subset of the full framework to work with, and often it can be frustrating and even crippling for a project. Version 2.2 of our award-winning, industry standard libraries for .NET Compact Framework helps bridge the gap between the .NET Compact Framework and the .NET Full Framework...
http://opennetcf.com/Products/SmartDeviceFramework/tabid/65/Default.aspx
10.OpenNETCF Advanced Debugging Toolkit (ADT)
Advanced Debugging Toolkit -- Addins and libraries to enable faster, more efficient debugging of .NET Compact Framework applications...
http://www.opennetcf.com/FreeSoftware/tabid/84/Default.aspx
11.OpenNETCF.Desktop.Communication
The Desktop.Communication Library contains classes used for communicating with a CE device from a PC such as Microsoft's Remote API (RAPI)...
http://www.opennetcf.com/FreeSoftware/tabid/84/Default.aspx
12.OpenNETCF Smart Device Framework v 1.4
Targeting Compact Framework 1.0 and Microsoft Visual Studio 2003
http://www.opennetcf.com/FreeSoftware/tabid/84/Default.aspx
13.Mobile Ink
The Mobile Ink Library is a .NET component that provides support for the new Windows Mobile 6 WISP Lite API in your .NET Compact Framework applications...
http://www.opennetcf.com/FreeSoftware/tabid/84/Default.aspx
14.OpenNETCF QRCode Library for .NET Compact Framework
The OpenNETCF QRCode Library is a .NET Compact Framework component that allows developers to decode QRCode images on a Windows Mobile or Windows CE device...
http://www.opennetcf.com/FreeSoftware/tabid/84/Default.aspx
UPDATE
15. 32feet.Net
by Peter Foot
A shared-source project to make personal area networking technologies such as Bluetooth, Infrared (IrDA) and more, easily accessible from .NET code. Supports desktop, mobile or embedded systems. The project currently consists of the following libraries:-
http://www.codeplex.com/32feet/
YET ANOTHER UPDATE
16. Mobile MVC Framework
by Alex Yakhin's
Model-View-Controller Framework for mobile devices running .NET Compact Framework 3.5.
http://www.codeplex.com/MobileMVC
17.Windows Mobile Unified Sensor API
by Kuosh
The Windows Mobile Unified Sensor API allows developers to easily access the hardware sensors that are available on various phones.
Sensors supported: Light Sensor,Capacitive Touch Pad,Accelerometer
Devices:HTC Touch *,Samsung Omnia/Instinct
http://www.codeplex.com/sensorapi
Did I miss something? Ping me if you know other useful non-comercial third party managed libraries