Investing in Index Funds – I use Vanguard for this, but there are several reputable sites out there that allow you to do the same thing.  It’s a good way to invest excess cash that you don’t need now and use it to diversify your portfolio.  I’m not going to make a specific recommendation here, but Vanguard does have a page that will make a recommendation to you based on your risk tolerance.  This is generally going to require more up-front money than Lending Club (probably $1,000+), but if you have the money, it’s something to consider.

One of his favorite tools is Personal Capital, which enables him to manage his finances in just 15-minutes each month. If you sign up and link up an investment account with $1,000+ within 40 days, you get a $20 Amazon gift card. They also offer financial planning, such as a Retirement Planning Tool that can tell you if you're on track to retire when you want. It's free.
Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.