Since the financial crisis, the IPO market has been a yawn.  But as the equities markets improved over the last six months, investors have been warming-up to public offerings.

In some cases, the returns have been stunning.  Just last week, the car-sharing service, Zipcar (NYSE: ZIP), saw its shares spiked 56% on its first-day of trading.  Some other hot ones include Qihoo 360 Technology (NASDAQ: QIHU), Dangdang (NASDAQ: DANG) Youku (NASDAQ: YOKU).  All have posted 100%+ returns.

So how can individual investors get these types of gains?  Unfortunately, it’s nearly impossible.  For the most part, Wall Street banks allocate IPOs to hedge funds, institutions and wealthy investors.  It’s a way to make their top clients happy.

Despite this, there are still opportunities for individual investors.  Keep in mind that – if a company is a game-changer – there should be ample long-term gains.  After all, this was the case with companies like Google (NASDAQ: GOOG), Salesforce.com (NYSE: CRM) and Chipotle Mexican Grill (NYSE: CMG).

And lately, there have certainly been some standout offerings.  Let’s take a look:

ServiceSource IPO

Founded in the late 1990s, ServiceSource (NASDAQ: SREV) has been able to build a solid business.  ServiceSource helps companies manage their revenue streams, such as from renewals, maintenance and subscription agreements.

The fact is that this can be a difficult process.  But to make things easier, ServiceSource has developed a suite of cloud-based technologies to automate things.  Yet the company also realizes that it needs to provide high-end services.

The ServiceSource platform is a global offering, which is translated into over 30 languages.  It also is available for a variety of industries like technology, life sciences and healthcare.

From 2008 to 2010, revenue increased from $100.3 million to $152.9 million.  Thus, ServiceSource trades at about 5 times revenue.  While this may seem pricey, it is actually much cheaper than other cloud operators.  Consider that Salesforce.com is trading 10 times revenue and SuccessFactors (NASDAQ: SFSF) is selling at a 14 multiple.

GNC Holdings IPO

Of course, GNC Holdings (NYSE: GNC) is a leading specialty retailer for health and wellness products.  On a global basis, it is a dominant player, with over 7,200 locations.  Actually, the company is 12 times larger than its next largest rival.

The large scale means that GNC has much leverage in getting lower costs.  But the company has also invested heavily in creating premium product offerings, which get strong margins.  These include Mega Men, Longevity Factors, Pro Performance and Ultra Mega.  GNC-branded products accounted for $850 million in revenue last year.

No doubt, GNC realizes that the Internet is a lucrative channel.  To this end, the company revamped its website in 2009.  So far, it has been gaining traction, in terms of traffic and conversion rates.

Total revenues for GNC have been growing at a steady rate, going from $1.67 billion in 2008 to $1.82 billion in 2010.  The EBITDA is a hefty $259.4 million.

The company is selling at 17 times earnings (for the past 12 months).  This is certainly a reasonable valuation in light of the company’s premium brand, global footprint and long-term growth potential.

Renren IPO

The company recently filed for an IPO and the shares should start trading within a couple weeks.  The proposed ticker is RENN and the price range was set at $9 to $11 per share.

Renren is the leading social networking site in China.  There are roughly 117 million activated users and the growth rate is about 2 million users per month.

Like Facebook, Renren allows its users to connect with friends, play games, listen to music and even shop.  Interestingly enough, the company recently launched jingwei.com.  It’s a professional network, which is similar to LinkedIn.

Of course, Renren’s growth has been sizzling.  Net revenues spiked from $13.8 million in 2008 to $76.5 million in 2010.  That’s a compound annual growth rate of 135.7%.

True, Renren is losing money.  The net loss was $61.2 million last year.  Then again, the company is focused on growing its operations – not generating cash flows.

It’s a good bet that Renren will have a strong opening when it hits the US markets.  Because of this, investors should wait a week or so to get a sense of the direction of the stock before making a trade.  Expect lots of volatility.

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