I'm pretty good with PHP these days, but it may be advantageous to learn Ruby down the road a bit (probably several months before it might even start to be on my plate). Just wondering if anyone has any suggestions on books, web sites, whatever that can help me learn syntax, idiosyncrasies, tricks, etc. of Ruby and Rails without spending a lot of time trying to teach me general programming concepts (other than how those concepts might be specifically addressed within Ruby).