Want to SharePoint from your WP7 App? Check out the SharePoint 2010 Windows Phone 7 Toolkit

Microsoft UK Faculty Connection - SharePoint 2010 Windows Phone 7 Toolkit

"I have been asked a few questions recently regarding developing Windows Phone apps which can access Sharepoint 2010 resources.
The easy answer is… download the following toolkit on CodePlex, the toolkit will help simplify the task of building Windows Phone 7 applications based upon SharePoint 2010 servers running Forms Based Authentication. This toolkit also allows you to use the same libraries to build Silverlight desktop applications.
This first release requires your SharePoint 2010 installation to support Forms Based authentication but once you do that, building applications is fairly trivial.
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Codeplex - Windows Phone 7 SharePoint Tool Kit

"The Windows Phone 7 SharePoint Tool Kit project will allow you to build Silverlight applications (both in Windows Phone 7 and the Desktop) that will do the following:

1. Authenticate against a SharePoint server configured to use Forms Based Authentication
2. Download, filtered and sorted lists
3. Display an auto generated data-driven from for editing list data that is based upon the metadata as provided from SharePoint.

This version is code-complete and working for the first feature set, but needs to be tested for edge-case scenario's.
To use this code base with your application, simply review the sample implementation and make sure you modify the following parameters on Common.cs in the library projects.

1. WebId - The unique identifier for the SharePoint web site you will be accessing.
2. SiteAddress - Full web address for your SharePoint server to include the name of the sub-site in the format http[s]://[WWW.YOURSITE.COM]
3. SubWeb - If you aren't connecting to the root web, you can put the path here. Omit the opening forward slash
4. Lists - Upon startup of the application, the MetaData for the lists are downloaded from the server. The names of the lists used in your application should populate this list.

The libraries that you download have default values that can be used as an example to work with your SharePoint server.
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I like having a library to access SharePoint without having to grab the assemblies off a machine with SharePoint installed...
But something to consider is the OData Support that comes with SharePoint 2010. That's another "Dev against SharePoint" avenue that doesn't require the SharePoint assemblies. In any case, am not watching this Project... :)