The Forbes list of the 400 wealthiest Americans -- only billionaires need apply -- is still topped by Microsoft founder and Chairman Bill Gates. He weighs in with $59 billion, up from $56 billion at the end of 2006.

But, as Forbes notes, Gates' days at the top of the world's heap of rich guys may be numbered. As some have already estimated this year, Mexican magnate Carlos Slim Helú is gaining on, and may have surpassed, Gates in wealth. Forbes pegs Slim's total on par with Gates'. As we noted this summer, Gates is giving away his money much faster than Slim.

The latest Forbes list has Warren Buffett as the second-richest American, with $52 billion.

Other Washingtonians on the list:
11. Paul Allen, Microsoft, $16.8 billion
16. Steve Ballmer, Microsoft, $15.2 billion
35. Jeff Bezos, Amazon.com, $8.7 billion
135. Craig McCaw, McCaw Cellular, $2.8 billion
239. James Jannard, Oakley, $2 billion
380. Timothy Blixseth, timberland, real estate, $1.3 billion