 <p>You seem to have two questions. </p> <p>The second is the more specific question regarding AjaxControlToolkit.dll. For that, take a look at <a href="http://stackoverflow.com/questions/7695657/error-could-not-load-file-or-assembly-ajaxcontroltoolkit-or-one-of-its-depende">ERROR Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies</a>.</p> <p>As to your original question, as long as you only need to deploy the DLL (in other words, you don't need to run an install program, modify the web.config, etc), the way to go is to place your DLL into your WSP solution package. This is easier than ever with Visual Studio 2010. For more information, see <a href="http://msdn.microsoft.com/en-us/library/ee231595.aspx" rel="nofollow">How to: Add and Remove Additional Assemblies</a> and <a href="http://blog.mastykarz.nl/including-additional-assemblies-wsp-visual-studio-sharepoint-development-tools/" rel="nofollow">Including additional assemblies in the WSP with Visual Studio SharePoint development tools</a>.</p>