I had a post earlier on silverlight 2 and the tooltip service. With beta 2 the game has changed, slightly... first buttons and other controls lost the tooltip property. Meaning you cannot simply say Tooltip="Hello World" like before. Now all items including layout controls like canvas, graphic elements like rectangle, and even controls like button all use the tooltip service. They made a tooltip service much easier to implement by removing the need for referencing the control dll like in beta 1. Now all you have to do is the following:

1. In the object you want to add the Tooltip functionality, inside its container specify the tooltip service; however, the tooltip property of the tooltip service wants to be set to an instance of a tooltip object and not a string:

<Canvas x:Name="SomeCanvas" Background="Green" Width="100" Height="100">

<control:ToolTipService.ToolTip>
     <ToolTip Content="Hello World" />
</control:ToolTipService.ToolTip>

</Canvas>


And viola, a canvas now has a Tooltip property.