Steve Jones (you may have heard of him ;-)) mentioned that there is book called Learn Windows PowerShell 3 in a Month of Lunches[/url] which, if I recall correctly, some people praised.

Aside from that I tend to do the opposite of what you should do in real life i.e. try and use PowerShell to achieve everything (within reason). My thinking is that practice and discovery in this way will improve your skills. I am certainly NOT advocating employing PowerShell for every task in production, however, any task that can be achieved in a non-production environment will aid your learning even if there is a more appropriate technology or method. In fact recognising that something else would have been a better solution has value too!!!

Also I tend to search for specific solutions to particular problems which I build up myself (just through standard search engine usage).