Upwork: This website offers a great marketplace for selling just about any professional service. You don't need a merchant account, website of your own or anything else for that matter. All you need to do is be able to provide a high-quality service at a reasonable price. But be informed, you will have to compete with many others that are constantly bidding on open jobs.
In the past few years, craft marketplaces have popped up all over the Internet and offer a place where you can sell your handy work to those who appreciate handmade items. Etsy is the most popular marketplace out there. You can create your own web store on this site and list your handmade crafts, vintage items, and craft supplies. There are plenty of other sites on the web that cater to arts and crafts of all types. You can earn some extra money while enjoying your favorite hobbies.