FREELANCE SERVICE SELLING : You can sell Development, Teaching, Marketing, Graphics & Designing, Video, Animation & Editing, Writing & Translations, Business, Video & Music etc.. If you are master in any skills then you can sell your service online.
DIGITAL DOWNLOADS/FILES/CODES: You can sell your softwares/codes/files.
WEBSITES/DOMAIN NAMES: You can sell your Starter/Established Websites, Domain Names. If you have good domain name( Brandable/Premium Domain Names) then buyer will love to buy at good price.