I found this blog post “My SharePoint Development Tools” which list many useful SharePoint development tools. Few of them are must for each developer. Please check it out at - http://blogs.pointbridge.com/Blogs/morse_matt/Pages/SharePointDevelopmentTools.aspx.
ISSUE: Recently I faced this issue that when I try to deploy my WebPart. Unable to add selected web part(s). WebPartName: Cannon unregister UpdatePanel with ID ‘ctl00RTMPanel’ since it was not registerd with the ScripManager. This might occure if the UpdatePanel was removed from the control tree and later added again, which is not supported. Parameter name: updatePanel. I faced this issue twice and both the time the issue was not what display here. This could be sure to any error in the WebPart. Following are list resolution from multiple instances. RESOLUTION: 1. Check the WebPartName.webpart file. Check whether you have a proper PublicKeyToken value. When I face the issue the value was PublicKeyToken=$PublicKeyToken$. If you have used WSP builder then in the Visual Studio you will find this file at \WebPartsProject\12\TEMPLATE\FEATURES\WebPartName\WebPartName.webpart. Sometime when you create a new WebPart using WSP builder then you do not get