Microsoft has thousand of pages about Windows XP SP2 and I think it's really difficult to read all of them and understand well all the SP2 features.
So, to help the process of well understanding the new XP SP2 features and benefits, I want to publish the great work of Mark Minasi: XP Service Pack 2 Highlights, Tips and Tricks, a great and detailed presentation of all the "Big Pack".
I recommend to read it... it's the best presentation I've read about the new XP SP2 (also a PDF is available HERE).
A little interesting tip to remember:
USB Key drive some security folks crazy because they're so small physically and so big storage-wise; what's to keep people from popping a USB drive into a USB slot, copying corporate data and walking out the door?
For the USB-paranoid, SP2 includes an ability to let users read data from a USB drive, but not write data to that drive. It's a simple Registry change.
- First, create a whole new key: HKLM\System\CurrentControlSet\Control \ StorageDevicePolicies.
- Then create a REG_DWORD entry in it called WriteProtect.
- Set it to 1 and you'll be able to read from USB drives but not write to them.
Wonderful! 
This morning I arrived on my office, turn up my PC and the first news I've read is this: Skype has released the first version of its software for Pocket PC platform.
Really wonderful... the power of Skype now is also on a mobile device. I was out from the Pocket PC world, but maybe now is arrived the time to buy one of these "toys"?