The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.

By Louis Navellier,



) -- Let's face it, this is America, and we like getting a lot for a little (hence the prevalence of dollar stores and all-you-can-eat buffets in this great nation of ours). Investors also like getting a lot for a little, which explains the popularity of

penny stocks.

Who wouldn't like the chance to turn their spare change into a small fortune? And unlike most established companies with fairly steady share prices, penny stocks afford you the opportunity to make a massive amount of money in a short amount of time. Of course, the trick is picking the right penny stocks to buy.

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The stocks on this list might not be what you would consider "true penny stocks." But in any market, and especially in a volatile, headline-driven one, micro-cap pink sheet or OTC stocks that cost only a few cents per share are incredibly risky investments. The companies on this list are super cheap, but they also carry market caps of $100 million or larger, making them much safer bets.

Here are 10 top penny stocks to buy now:

Uranium Resources Inc. (URRE)

Uranium exploration, mine development and production company

Uranium Resources Inc.


has watched its stock value skyrocket 179% in the past 12 months -- and it is still trading for less than $2 per share! This is even more impressive when you consider that investors fled the sector in March after the nuclear power plant crisis in Japan, causing URRE to lose close to 50%. Since its March 16 low, shares have climbed 38% to $1.92. With a 52-week trading range of 38 cents to $3.98, look for shares to make their way higher as the sector continues to rebound.

Japan nuclear power plant

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Sprott Resource Lending (SILU)

Formerly known as Quest Capital Corp.,

Sprott Resource Lending Corp.


has returned 40% in the past year, and is currently trading at $1.78. SILU has had an up-and-down year, but this penny stock has the potential to bring you fast gains. During a two-day span in early April, SILU jumped 13%.

AEterna Zentaris (AEZX)

AEterna Zentaris Inc.

(AEZS) - Get Report

, a drug development company specializing in oncology and endocrine therapy, has seen its stock value increase 55% in the past 12 months. Up over 8% since the start of January, AEZA is sitting at $1.90.

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RAE Systems Inc. (RAE)

RAE Systems Inc.


develops and manufactures radiation and chemical monitors. Since the nuclear crisis in Japan, the company has ramped up production of its radiation-detection products. Currently trading at $1.87, the stock has also ramped up, climbing 16% year to date. And it is up an impressive 116% in the past year.

Cardero Resource Corp. (CDY)

Cardero Resource Corp.


is down about 18% since the start of 2011, but shares are still up 50% in the past six months. Currently at $1.80, this mineral exploration company is a penny stock worth buying with a 52-week range of $1 to $2.37.

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Sirius XM Radio (SIRI)

Satellite radio broadcaster

Sirius XM Radio Inc.

(SIRI) - Get Report

is popular among penny stock investors. At $1.83, SIRI is up 67% in the last year, and 20% since mid-January. Investors should also note the company's quarterly revenue growth of 9% from last quarter.

Capstone Turbine Corp. (CPST)

Next on our list is

Capstone Turbine Corp.

(CPST) - Get Report

, which develops, manufactures and markets microturbine technology solutions. Currently at $1.69, in the past six months, CPST stock has jumped 122%. This penny stock also posted quarterly revenue growth of 51% year over year in its last income statement.

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Kimber Resources (KBX)

Exploration-stage gold and silver company

Kimber Resources Inc.


has gained 26% year to date, and is up 58% in the past year. At $1.67, this penny stock is worth a close look for potential investors. The stock's 52-week range is 60 cents to $2.17.

UR-Energy (URG)

Junior mining company

UR-Energy Inc.

(URG) - Get Report

has watched its stock increase 73% in the past 12 months. Currently trading at $1.64, URG has more than doubled its 52-week low of 73 cents, and is a great choice for penny stock investors.

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Gold Reserve (GRZ)

Last on the list is exploration-stage company

Gold Reserve Inc.


. In the past 12 months, this penny stock has outperformed the broader markets to the tune of a 58% increase. More recently, GRZ is up 16% in the past six months, trading at $1.77.

>>To see these stocks in action, visit the

10 Cheap Stocks to Buy for Under $1.99

portfolio on Stockpickr.

As of this writing, Louis Navellier did not own a position in any of the stocks named here.

One of Wall Street's renowned growth investors, Louis Navellier is the editor of four investing newsletters: Emerging Growth (formerly known as MPT Review), Blue Chip Growth, Quantum Growth and Global Growth. His longest-running publication, Emerging Growth, has a track record of beating the market nearly 3 to 1. Navellier is the author of a BusinessWeek bestseller, "The Little Book That Makes You Rich," and the chairman and founder of Navellier & Associates, Inc.