Make money on YouTube. People who love the spotlight and have other online hustles should consider creating their own YouTube channel. If you’re interested — and interesting — you can use the platform to market affiliate products, sell products you create yourself, or receive ad revenue for your informal tutorials or entertaining videos. Once you get the ball rolling, YouTube offers a partner program that can help you monetize your business further.
The more online clout you have as a business, the more money you’ll make. If you’re known for making lasting connections (as is the case with GetVoiP above), then you’ll have no issues building your online brand. You’ll be recognized in your community and begin to build a buzz in your industry. Tracking your numbers (how many people view your site, click each ad, and make a purchase from that click) gives you the leverage to expand this part of your business, enabling you to continue building your online rep.
Buy and sell domain names. If you’re good at finding popular yet undiscovered domain names, you can make some cash on the side by buying and reselling websites. Think of it as digital real estate speculation. Domains are available on GoDaddy.com for as little as $2.99 per year, but are sometimes resold at far higher prices: According to Business Insider, the site MM.com sold for $1.2 million dollars in 2014. Once you find the perfect domain name to resell, you can market it on Flippa.com for a flat fee.
Creating space for banner ads on your website is another way to generate a revenue from adverts. However, for this type of advertising, you will need to contact businesses directly and ask them if they would like to advertise on your website. The upside is that you can charge a set amount, or even a recurring monthly fee, to business to promote their services on your site. Using a WordPress plugin like AdSanity is an effective way to manage this type of advertising.
Find a profitable niche. Starting with your interests, write down as many niche ideas as you can. Think about topics people might search online. Ideas include passions (like surfing or body building), fears (like spiders or speaking in front of crowds) and problems (like getting out of debt). Do keyword research to see it others are interested in the topic. Find out if a domain name is available that matches the keyword 100 percent. 
A blog highlights your technical ability and showcases your ability to write blog posts. Your blog can be about different topics than those you write about for your clients. In fact, it should be on a topic that interests you. Visitors will see that you can not only write, but you can also build an online community. A good blog has the potential to earn you many referrals for more clients.
The money is most certainly in the list. If you're at all interested in online marketing, setup email software and create a lead magnet that you can use in your sales funnel. Then, build up that list. It's often said that you can expect to earn about $1 per subscriber per month. If you have a list of 10,000 subscribers, that means you can earn roughly around $10,000 per month. You will need to deliver value and not pitch them on every email, but it is a very achievable goal in a short period.
If you love to travel and find yourself randomly searching for airfare sales or browsing Lonely Planet, why not carve out a niche for yourself as a private travel agent? My friend, Mark Jackson did just that, making extra money online with his travel consulting side business. Start with word of mouth recommendations from friends who know they can count on you for the cheapest flights, and then move on and create a Facebook or LinkedIn group to invite people who want to stay on top of the latest deals. Eventually you could spin this into a full-time consultancy teaching people how to make their dream trip a reality.