Passive Income through an Index Investing Portfolio
Don't be so quick to ignore this approach as it may seem boring but this is a topic I have written about extensively on Passive Income UK's sister site Index Investing.
You may not think investing is for you but look at it this way. If you can construct a collection of funds consisting of income paying share and bond indexes, you'll be able to generate your own passive income.
The old rule is money begets money, so if you already have a pile of cash sitting there collecting dust in a low-interest current account, you may want to see if you can put it to better use elsewhere. Sites such as Monevator have already done a sterling job covering this topic.
This method is as simple as it is well tested. Since you want your income to be passive, I would suggest only going with index funds using a company such as Vanguard or BlackRock. All you'll need to do is set up an automated monthly payment into a series of diversified funds and let the miracle of compound interest take over.
It's important to note you'll only want to take on as much risk as you are comfortable with and if you have any questions you should consult a financial professional. I am a mere armchair amateur with a passion for index funds!