The 7 hottest FinTech companies in Silicon Valley

Square is a software platform that enables retail stores and restaurants to accept mobile payments via iPads, iPhones, or Android devices.

Jack Dorsey, the company's founder and CEO, is also currently serving as Twitter's interim CEO; just after news broke that Dorsey would step in at Twitter, reports surfaced that Square was planning to go public. Sources say the company may have already filed a confidential registration document with the SEC, which is permitted for companies with less than $1 billion in revenue.

Square's most recent round came in late last year, when it raised $150 million at a reported $6 billion valuation.

Lending Club is one of the world's biggest online lending marketplaces. Last year, Lending Club's IPO was the largest among all US tech companies. Renaud Laplanche, the company's CEO, founded Lending Club to let people provide low-cost financing to their peers. Now, it lets institutional investors do the same.

The online credit marketplace raised $870 million in its IPO last December. It's valued at more than $7 billion.

In September, Apple announced partnerships with a number of retailers and payments companies for its Apple Pay service. Among them was Stripe, a five-year-old mobile-payments startup. According to its website, Stripe currently powers businesses out of nine global offices in 20 countries. The company focuses on beautiful code and design to create user- and developer-friendly experiences.

Recently, Stripe has been in talks to raise a funding round that could see the payments company, which has previously raised $190 million in funding, reach a valuation of $5 billion.

Robinhood, a sleek mobile-brokerage app, is making it possible for anyone to invest — not just Wall Streeters. Unlike rival investment apps E-Trade and Schwab, which charge $7 to $10 per trade, Robinhood is free to use. In May it raised $50 million in a funding round led by New Enterprise Associates. Previous investors include big-name VCs and celebrities, like Snoop Dogg.

Inspired by the Occupy Wall Street Movement, cofounders Vlad Tenev and Baiju Bhatt created the app to "democratize access to the financial markets." And good news for their mission: It’s now available for anyone to use.

Enigmatic startup 21 Inc. wants to bring bitcoin to the masses through an embeddable chip for phones that will allow users to "mine" bitcoin in the background. Though the company only recently announced its master plan, it's been building capital for some time. In March it raised $116 million in venture funding from investors including Andreessen Horowitz, Yuan Capital, and RRE Ventures.

21 Inc. recently shook up its management as well: Cofounder Balaji Srinivasan, who is also a partner at Andreessen Horowitz, is taking over as CEO, and Matthew Pauker, the current CEO, is replacing Srinivasan as chairman.

Despite slumping bitcoin prices, Coinbase — a digital wallet used to buy and manage the digital currency — is on the rise.

The startup raised a $75 million round in January, a record-breaking amount for a bitcoin company at the time. Investors include the New York Stock Exchange, Andreessen Horowitz, and banks USAA and BBVA. The round supposedly puts Coinbase’s value at $400 million.

Last July, Twitter purchased mobile-payment system CardSpring, marking the social network’s foray into real-time commerce. CardSpring helps developers write applications that accept credit-card payments, creating a world of opportunity for Twitter; its programs can potentially allow users to download discounts or make purchases through Tweets.

In 2012, CardSpring raised $10 million in Series A funding from investors Techammer, Greylock Partners, and Accel Partners.