News from the pharmaceutical giant Pfizer (PFE) could quickly stop the downward slide of that company's shares.

Early tests of Pfizer's cancer drug crizotinib, while only preliminary, have generated a fair amount of excitement among cancer treatment researchers. The drug, which targets a genetic factor among specific lung cancer patients, has reportedly been shown to reduce the size of tumors caused by that disease.

UAL Corporation (NASDAQ: UAUA), the parent of United Airlines, got beat up pretty good along with the rest of the airline group yesterday.

However, investors should not stampede away from this sector, or more specifically, from UAL. As discussed in a Bear Stearns report released yesterday, the airline, which recently emerged from bankruptcy, continues to explore ways to utilize its massive cash hoard of $5 billion to maximize shareholder value, $1 billion of which management believes is excess cash.

Also, UAL is seeking ways to unlock value for its Mileage Plus program, a business that generates $800 million per year in revenue and has a large deferred revenue stream which provides some visibility for future revenue. Aeroplan, the Canadian-based loyalty marketing service business that was spun off from Air Canada's holding company, sells for a 60% premium to its former parent and a 200% premium on an enterprise value/EBITDA basis to the pure airline, Air Canada.

The Bear report places a $65 price target on UAL, with the asset break-up value of the company going as high as $80. Operational turnaround, huge free cash flow generation and the potential to realize value for the mileage plus business are all cited as reasons that could lead to a considerably higher stock price.

According to a source of Bloomberg, Goldman Sachs (NYSE: GS) is going to cut the expenses and performance fees on its poorly performing hedge funds. The source reported that "new participants won't pay the 2 percent management charge and Goldman will cut its performance fee in half."

This is a very interesting move for a company that claimed the recent $3 billion infusion was capitalizing on an investment opportunity, not a rescue. It would seem like the company is cutting management fees to prevent being forced into further "capitalizing" on this investment opportunity.

In my opinion, this whole debacle is just a bump along the way for Goldman's funds. Goldman Sachs is an incredible fund manager and business (as displayed by the stock's performance since coming public) and I think that, over the long term, funds such as Global Alpha will recover and flourish.

I think the sell-off in Goldman's shares has created a buying opportunity and I reiterate what I said about a month ago here. The fact that this stock has sold off nearly as much as problem-ridden Bear Stearns (NYSE: BSC) simply due to poor hedge fund performance (Bear had two blow-ups) is simply ridiculous.

As you can see from the chart to the right, I've been wrong on this call so far, but hedging with the Vanguard Financials ETF (NYSE: VFH), as I suggested would have reduced your losses.

• Read about the exit of Goldman Sachs' star Mark McGoldrick

The current stock market correction has created a nice buying opportunity for eBay Inc (NASDAQ: EBAY). After reporting strong 4Q06 results, the stock has corrected as much as 10%.

Morgan Stanley's Mary Meeker said in a report released yesterday that eBay's strong operating performance is continuing into 1Q06 and is tracking ahead of her estimates.

Meeker forecasts strong ASP and conversion rate for sellers which will translate into better pricing and higher profits.

Volume, pricing and conversion improvement will translate into massive cash flow generation for this eBay. Remember, eBay's stock has corrected from a high of $46 per share. That is a sizable correction for this Internet leader.

Guest blogger and avid investor Bob Sirmans offers this perspective on recent market events:

Conventional wisdom used to support the notion that market downturns were buying opportunities and investors should use them to add to or open new positions. It seems to me that the tech wreck of the early 2000s has changed how people invest and their views on markets. Now it's not quite so clear that a downturn is necessarily a good time to buy.

However, in spite of the fears that people have, I can't imagine not using dips/corrections as a good time to buy. I used the market spiral yesterday to open a new position in a stock I've been looking to buy to give me more exposure to American companies that generate a least 1/2 of their revenue (on a percentage basis) from outside the US. Yesterday I bought some Caterpillar Inc. (NYSE: CAT) on the market slide.

The way I see it, the US and China economies are both showing signs of slowing. While I think this will rattle the markets, putting money in the bank isn't what I want to do.

Am I more likely to take profits now? Absolutely. But I still need to keep my money working.

Does anyone else still view market downturns as a buying opportunity?

With eBay's stock price under $35 and only a few dollars from its 52-week low ($31.20 on April 27, 2005 ... if you're counting), it could be a good deal. Do I hear the words, "buying opportunity"? It's definitely been selling these past few days, with volume more than 50% higher than average and prices slowly falling. At just over 45 times, the company's P/E ratio is pretty high. But it's been way higher and it's no less of a great company than it was two years ago.

It seems that, every day, more people use Paypal and Skype, and someone else tells me they'll check for a skein of handpainted yarn or a used cell phone on eBay instead of buying it IRL. Who wants to get in the car and go shopping, after all? (Not to mention: you'll save gas. Always a good thing.)

There are always two questions I ask when I'm thinking about the future prospects of a stock; one is am I spending my own money there? and the second is, do I believe in the management team? The answer to both questions, for me, is still "yes." I think I'd wait until eBay dips a bit lower, but under $35 is definitely a sweet spot for me.