A spin-off for web designers is to offer a landing page creation service. Well optimized landing pages can be the difference between a successful and a failing business. And, as creating the perfect landing page isn’t easy, this is a service many businesses are prepared to pay for. I know people who are earning 6 figures per year and all they do is create landing pages for businesses. There’s serious money to be made.
This is slightly different than eBay Arbitrage. Find a distributor that will sell to you at their discounted prices. List these items online. Buy and ship to your heart's content. Basically, you become a reseller of computers and other hardware. Another thought here is to sell computer parts. Can you find a part that seems to be in demand? If you can supply the demand, you may just have yourself a part-time business.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.