Up until the credit crisis, private equity firms had it made. They had plenty of leverage to play with and could load up their acquisition targets with it. So, they could realize a fantastic return on equity, mitigate their own risks, and show that they were the studs of the Street.

Then, all that went away. Credit markets dried up, and private equity companies lost their acquisition fuel. The numbers aren't as big as they used to be, but it looks like the private equity market is back in action.

A123 Systems (NASDAQ: AONE) got its start back in 2001 in Dr. Yet-Ming Chiang's laboratory in MIT. Along with two others -- Gilbert N. Riley, Jr., and Ric Fulop -- he saw a huge opportunity to build new battery technology. While it took six years to hit the market, it was well worth the effort.

After an excruciating dry spell, the IPO market is ready for lots of action this week. It looks like the equities markets are finally recovering from the financial implosion that began last September.

From 2004 to 2008, the number of vehicles sold at auctions in the U.S. ranged from 9.4 million to 9.7 million per year. And there are no signs that this will change.

With a name like rue21, the company must be cool, right? Well, it is. rue21 is a specialty apparel operator that is focused on the fickle young crowd -- that is, those between 11 and 17 who want to look "21." Or, for older people who want to feel "21."

While the IPO market has been meager over the past year, there still have been some bright spots, such as the offerings of e-learning companies. Some of the notable deals include Bridgepoint Education (NYSE: BPI) and Grand Canyon Education (NASDAQ: LOPE). The shares of both companies are up over 40% since their IPOs.

While eBay (NASDAQ: EBAY) said earlier this year that it was planning to spin off Skype in an initial public offering in 2010, it is now being reported that eBay is looking for a buyer willing to pay $2 billion or more for the internet telephone service provider.

Over the past few months, one of the hottest sectors has been the financials. And to capitalize on things, Wall Street is looking to the IPO market. So, this week Plains Capital Corp. filed to go public, planning to raise $140 million.

In the wake of last week's public offering of Dollar General, more IPOs are expected to be coming down the pipeline as private equity firms seek a monetary return on investments made during the boom years. Speculation is that Toys "R" Us and Dunkin' Donuts could be next.