Companies are willing to pay for advertising space on personal vehicles, especially if you drive frequently and in populated areas. This passive income method can be quite lucrative with minimal effort. Wrapify or Carvertise are companies that connect drivers with advertisers looking to pay for car ad space.

With people seeking more connections online, you can get paid to be someone's virtual friend, chatting, playing games online, or offering virtual companionship. Websites like RentAFriend or FriendPC allow you to offer companionship services and get paid to be a virtual friend.

Donating plasma is not only a way to contribute to a good cause but also a means to earn some extra cash. Regular donations can bring in a steady monthly income. BioLife Plasma Services or CSL Plasma are centers where you can donate plasma and receive compensation.

If you're comfortable with it, participating in clinical research trials can pay well. These trials look for healthy volunteers to test the safety and efficacy of treatments or medications. ClinicalTrials.gov provides a searchable database of clinical studies worldwide, where you can find trials seeking participants.

Many parents look for reliable childcare during evenings or weekends. Offering specialized childcare services during these off-peak times can command higher rates. Care.com or Sittercity are platforms where you can list your childcare services and connect with parents in need of nighttime or weekend care.

If you live in a desirable location, producers may pay to use your home as a film set. This can be a significant source of income for just a few days' work. Set Scouter or Giggster are platforms where you can list your home for film, TV, or photo shoot rentals.

Companies pay for you to shop or dine at their establishments and report back on the experience. This can include reimbursement for purchases or meals in addition to payment for your feedback. Market Force or Secret Shopper are companies that offer mystery shopping and dining opportunities.

While it may take time to build an audience, creating content about a unique hobby or interest can eventually generate income through ads, sponsorships, and affiliate marketing. WordPress or Blogger for blogs, and YouTube for video content, are platforms where you can start and monetize a niche blog or channel.

If you have extra space in your garage, basement, or shed, you can rent it out to people looking for storage options. This is a great way to earn passive income. Neighbor or SpareFoot allow you to list and rent out extra storage space in your home or garage.

If you have expertise in a specific area (no matter how weird!) create and sell an online course. With platforms like Udemy or Teachable, you can reach a global audience. Udemy or Coursera are platforms where you can create, publish, and sell online courses on various topics.