How many times have you kicked yourself for not buying an attractive investment? More than once, I've wished I had a time machine to go back and seize those opportunities. But who needs to break out the ol' flux capacitator when a stock market crash will do the job just as well? The market's strong decline over the past few weeks has made many previously attractive investments even more so.

Remember, stocks don't always fall for fundamental reasons. Sometimes they're just following the herd -- and sometimes, investors have decided to punish them way too harshly. Let's take a gander at a few companies that have earned high marks from our CAPS community of investors, yet fallen significantly in recent weeks.

Cheaper energy
Pengrowth Energy (NYSE: PGH), the Canadian developer and producer of oil and natural gas, has seen shares drop more than 20% over the past few weeks. One lovely side-effect of falling stock prices is that dividend yields rise; Pengrowth's yield recently ballooned beyond 8%. Despite fires, floods, and pipeline outages in Western Canada, the company saw its second-quarter net income jump nearly fivefold year over year.

If you don't believe that Japan's recent nuclear disaster will slow or stop the promise of nuclear energy, then you might want to revisit Denison Mines (AMEX: DNN). The company explores for and produces uranium, mostly in North America. Its stock got a roughly 25% haircut in recent weeks, though it's not any less likely to benefit from, among other things, the Chinese offsetting their coal-burning emissions with nuclear power.

Mining for dollars
Copper giants Southern Copper (NYSE: SCCO) and Freeport McMoRan Copper & Gold (NYSE: FCX) each lost more than 18% in recent weeks. Do their mines suddenly have 16% less potential? Not at all. Is demand for copper expected to fall by 16% in the near future? Nope. Are their operations expected to shrink soon? No -- Wall Street analysts actually expect Freeport to grow by an annual average of 15% in the coming five years, while Southern Copper is expected to average 21%. Freeport has dealt with some striking workers in a Papua, Indonesia, facility, but that's not enough to derail its future.

Drugs and equipment on sale
Many investors have been licking their chops over Elan (NYSE: ELN). Either they harbor high hopes for the drug it's developing to treat multiple sclerosis, or they think it'll get bought by Biogen Idec (Nasdaq: BIIB) or another bigger fish. Over the past few days, Elan shares have sunk by about 25% -- giving opportunistic investors a cheaper entry price.

MAKO Surgical (Nasdaq: MAKO) has fallen around 30% over the same period. It's developing equipment to help surgeons perform knee and hip replacements robotically. Sure, there are risks -- bigger competitors could always enter the business -- but those risks are not suddenly 30% stronger in recent weeks. If MAKO Surgical had piqued your interest before, you should consider looking at it more closely now, now that shares have traveled back in time to their earlier levels.

Positioned to win
If you fear you've missed your chance to buy great stocks at the right price, don't lose hope. A watch list of the stocks you love can help you be ready to pounce if they fall to a better price. Check your watch list regularly, and you'll notice when a stock of interest takes a tumble into more attractive territory.

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