Someone asked me to recommend a few books, so here they are:
1) Windows PowerShell Cookbook by Lee Holmes (from PS Team)
2) Windows PowerShell in Action by Bruce Payette (from PS Team)
3) For Exchange specific stuff, I actually haven't tried any (makes sense as we were writing code most of the time :). Here are a few I dug up on the web, they look promising:
In fact, a few guys I know wrote a very nice book that should definitely be on the top of the list.
Here's to more books, fame and fortune from these fine authors!