The enterprising citizens over at Dreamland Resort just clubbed together and bought a new satellite image of the USAF Flight Test Center's secret annex in Nevada, better known as Area 51 - see page 24 of this for a quick background brief, which is still pretty current.
Dreamland resort webmaster Joerg Arnu has posted the first excerpts from the image. with more to follow. He hasn't been able to determine at press-time whether we can post images ourselves, but we'll keep you posted.
If there's a trend visible, it's construction - including the biggest hangar yet, 360 feet wide, equipped with an earthern berm to conceal activities from the closest public vantage point, and the enlargement of the "scoot and hide" hangar near the runway.
The latter is not surprising, given the proliferation of imaging satellites that are not under US control. (Ikonos-2, which took these pictures, is not one of those satellites, which is why there are no secret airplanes to be seen,)
But the general expansion is not surprising either. Black budgets have boomed since 9/11. Projects that were what the late Skunk Works boss Ben Rich called UFOs (UnFunded Opportunities) in 2001 became serious candidates and competitions in 2002, risk-reduction activities in 2003 and funded items in 2004, and lo and behold, now there is hardware that has to be concealed.
In coincidence, the Center for Strategic and Budgetary Assessments has released an analysis of the 2008 classified budget for research, development and acquisition, by Steve Kosiak. The $18.1 billion total in FY2008 (the report explains how this total is legitimately arrived at) is far bigger than the total defense budget of most other countries; and the USAF's share of this money has now surpassed 40 per cent of the service's acquisition spending.
And, by the way, that's not all, by a long shot. Check this out from page 29 of the FY2008 operations budget:

$10 billion for "other programs"? That's a bit like putting a $26,000 deduction for "miscellaneous" on your tax return.
It's also important to remember that there is only one reason for a base like this: to flight-test hardware that is secret and visibly different from other aircraft. The considerable trouble and expense involved in operating at Groom Lake is not justified for testing some new targeting pod on an F-16 or a SIGINT fit on a Global Hawk.
So what is actually out there? Big hangars don't necessarily mean super-heavy aircraft - a long-endurance UAV with a big payload will have an impressive wingspan. Best guesses, still, include experimental platforms pushing the boundaries of stealth, particularly in terms of allowing aircraft to persist undetected around the clock, and experimental UAVs and UCAVs.
page 39, Bill ..... ;-)