Update: fixed the link. Thanks, Hanako Izumi.
C++0x is finally becoming real to me. I started demoing some C++0x features over a year ago; but now here is Visual C++ 2010 and it's just packed full of goodness. Does it have everything? No. Does any compiler? Good question.
Here is a handy table from the C++ team about what Visual C++ 2010 supports. The MSDN blog redesign seems to have borked the table a little, but the colours should probably be all you need if you know that the last column is VC10. Use View Source if you must know more. Scott Meyers keeps a spreadsheet, and is nice enough to export it out to the public web, covering gcc and VC, with handy links to more details on the features or a substitute (usually something from Boost) you can use if it's not there. He has plenty of helpful links on the cover page, too. There's also a wiki with less detail, but covering more compilers.
If you're wondering about the state of the standard, and whether x is going to end up being A, B, or C, your best bet is to read Herb Sutter's blog. He posted when the Final Committee Draft (FCD) was text-complete, and a pointer to how anyone can comment on it if they wish to.
If you haven't been paying attention, now's the time to catch up!