The JOBS Act mostly affects startups looking for investment, by eliminating a lot of red-tape associated with investing in companies, which is not necessarily a good thing. For those startups bootstrapping their way to success, it won't have much direct benefit.
The three main things to know about the JOBS Act:
It increases opportunities for equity investment. Though crowdfunding -- small-time Internet investment -- was not previously illegal, it had limitations. The JOBS Act removes those limitations. Most importantly, the JOBS Act allows small businesses to crowdfund equity investments, which should draw more investors into the trend.
It eases rules on public disclosures. Previously, private companies with over 500 shareholders and $10 million in assets were required to comply with SEC public disclosure rules. Startups often felt forced to file an IPO. The JOBS Act increases that number to 2,000 shareholders, which should give companies the ability to seek more funding and time to plan for an IPO.
It makes it easier to go public. The JOBS Act creates "emerging growth companies" -- those businesses with less than $1 billion in revenue. Emerging growth companies that wish to go public are exempt from some Dodd-Frank rules, and have fewer financial reporting requirements when filing an IPO.
The legislation also relaxes eligibility criteria for Regulation A, which exempts small securities offerings from certain SEC filing requirements. Congress has raised the exemption eligibility amount from $5 million in offerings to $50 million.
Here's another good breakdown of the main points in the JOBS Act.
For a counterpoint, take a look at this article, and this article, on why it is bad legislation.
Update: The JOBS Act was signed into law on April 5, 2011.