Optimism's back! Emboldened by stronger-than-expected earnings from eBay (Nasdaq: EBAY) and Dow component AT&T (NYSE: T), investors pushed the Dow Jones Industrial Average (DJIA) above 9,000 today for the first time since January. This milestone caps a good run for the index recently, which is up approximately 7.5% since the end of June.

Here are the five Dow components that have posted the highest returns since the end of June:

% Return Since June 30

2010e Price-to-Earnings Ratio

American Express (NYSE: AXP)

24%

20.1

Caterpillar (NYSE: CAT)

17%

23.3

Intel (Nasdaq: INTC)

16%

17.4

Cisco Systems (Nasdaq: CSCO)

15%

15.4

DuPont (NYSE: DD)

11%

14.0

Source: Author's calculations based on data from Capital IQ, a division of Standard & Poor's.

Will this strength continue? The only way I know to approach that question is by looking at valuations, so here's where we stand (based on yesterday's closing prices): Continued...