1. Dig up your unused gift cards, and sell them on sites like CardKangaroo and Raise. On the former, for example, you could net about $15 for sending in a $25 iTunes gift card.
2. Sell your photos on sites like Shutterstock, iStock, Getty Images and Adobe Stock. Depending on the site's starting royalty rates, you could earn 15 to 33 percent per photo.
3. Instead of keeping old smartphones and laptops in a drawer, sell your devices on sites like Decluttr and Gazelle. For example, a 256-gigabyte iPhone 8 Plus could earn you between $200 and $420 on Decluttr, depending on your carrier.
For more tips, check out Entrepreneur's article on quick ways to make extra cash without quitting your day job.