Let's party like it's 1938.

July was another great month for investors. You have to go all the way back to 1938 to find a healthier five-month run in the S&P 500. Most of us weren't even around 71 years ago, so for us, this is the greatest five-month rally of our lifetime.

Just do yourself a favor: Don't believe the hype. The market still has a lot to prove. There will be plenty of market-shaping events taking place in August, and you shouldn't assume that this vibrant rally is a lock to notch a six-month record. 

Here are a few of the days that I plan to approach with eyes wide open this month.

Aug. 6
Sirius XM Radio (NASDAQ:SIRI) reports its second-quarter results on Thursday. Some of the metrics won't be pretty.

  • The satellite-radio operator probably experienced more cancellations than additions during the past three months.
  • Analysts see revenue of $608 million, just 1% ahead of what Sirius and XM generated as stand-alone services a year earlier. XM rang up $318 million on the top line, with Sirius generating $283 million in revenue.
  • Wall Street sees year-over-year revenue declining during this year's third quarter, so this may be the near-term peak on the top line.

Thankfully for those long on Sirius XM, these same analysts see the radio giant posting a substantially narrower deficit this time around.

This is important, especially as Sirius XM sheds its growth-stock skin and becomes a play on improving operations. Thursday will be more about assessing the initial success of recent rate increases and smartphone downloads than about bellyaching over defections. The report will matter on many different levels, from one of Wall Street's most actively traded stocks.

Aug. 7
It's been nearly five months since Merck (NYSE:MRK) announced its plans to acquire Schering-Plough (NYSE:SGP) in a deal that was originally valued at $41.1 billion. There have been several "I object" challenges to the marriage along the way.

It may be too early to break out the wedding singer, but shareholders finally have a say on the nuptials this Friday. Merck investors will vote on the merger in the morning, and Schering-Plough stockholders will follow suit in the afternoon.

Consolidation in the pharmaceuticals industry has been an important trend in 2009. Friday's balloting is sure to validate the sector's direction, by pushing two of its biggest players one step closer to their honeymoon.

Aug. 12
Toll Brothers (NYSE:TOL) reports its preliminary third-quarter results a week from Wednesday, with the actual report following two weeks later, on Aug. 27. There are several reasons to pay attention to one of the country's leading residential developers.

  • Because Toll Brothers specializes in higher-end communities, it's an attractive gauge of the industry's pulse.
  • In an industry of overly leveraged weaklings, Toll Brothers' relatively sparkling balance sheet makes the builder a standout citizen.
  • Most of the developers that have posted quarterly results in recent weeks have come through with narrower deficits than they delivered a year ago. Toll Brothers is different. Analysts see losses widening, from $0.18 a share last year to $0.32 a share this time around.  

Toll Brothers also has one of the more charismatically blunt CEOs in the industry. If the residential real estate market is bottoming out or in the early stages of a recovery, Robert Toll will say so.

Aug. 25
There are several bellwethers reporting this month, with wide-reaching implications. Hewlett-Packard (NYSE:HPQ) reports on Aug. 18, for a great glimpse into the state of personal computing. And Tiffany (NYSE:TIF) steps up on Aug. 28. The upscale jeweler is the perfect proxy for big-ticket items as they relate to discretionary income.

But Staples (NASDAQ:SPLS) may provide an even more crucial test. I haven't confused the country's leading office supply chain's "easy" button with a panic button. I realize that Staples commands just a fraction of HP's market cap.

However, Staples offers a panoramic vista into the spending habits of companies of all sizes. If sales are up, corporations are feeling confident enough to add office furniture, upgrade office supplies, and order more toner cartridges.

Gauging the market's prospects really may be as easy as tapping that "easy" button.

Some other reads to get you through the month:

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Longtime Fool contributor Rick Munarriz needs to remember that his older sister's birthday is in August. He owns no shares in any of the stocks in this story and is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.