Victoria Bampton is truly the Lightroom Queen. She really knows the program and is very gracious about it.
But not everybody knows everything and for those other occasions I suggest:
http://www.lightroomforums.net/forum.php
http://www.luminous-landscape.com/fo...75cbc12a7483a&
The Lightroom forum is probably the best and it's where Victoria shows up regularly. When she doesn't have an answer, one of the Gurus will have it.
My favourite author is another Brit - Martin Evening. I have three of his books for three versions of LR.
Previous posters have made some very good suggestions for resources - Julieanne Kost has very good tutorials.
Also Laura Shoe:
http://laurashoe.com/category/tutorials-and-tips/
If you can get an XP machine to work with LR4, I would strongly recommend it - it has some much improved controls that were not in LR3. There is a Shadows slider now (for one) - it's so good, I'm going over all my files for the past six years and doing them over.
It comes down to the MP size of your sensor/files - I was fine with a 30D (8 MP), but when I acquired a 5DII (twenty-odd), the XP machine died. Having said that, often a disk clean and complete reinstall will give an old machine a new life. The XP machine I replaced (it's now a business machine) had a new MOBO installed earlier this year and the HDD was formatted and XP reinstalled, and I'm tempted to install LR4 on it to see how it performs.
Glenn