[xmonad] Changing workspace using the mouse

I'm interested in using the mouse to navigate between windows, while retaining the benefits of tiled window management (I hate resizing windows by hand). Xmonad already lets me change the focus within a workspace with the mouse. Is there any way (possibly using an extension or by interaction with an external tool) to use the mouse to switch workspaces? How about rearranging windows within a (tiled) workspace? I haven't found anything relevant in the documentation or the list archives, but I might not be searching for the right thing. If no such capability currently exists, do you have any tips on where I should start if I want to try writing my own? Thanks, -- Ian Leroux