It's not widely known that it's possible to sell services on eBay, in fact there's a large category devoted to it, called ‘Speciality Services'. To give you an idea of some of the possibilities, some of the main sub-categories include:
Advice & Instruction
Custom Clothing and Jewelry
Graphic & Logo design
Media editing and duplication
Restoration and repair
Web and Computer services
As you can see, there's quite a range on offer, and bear in mind that there are specific niches even within each of these main sub-categories. For example, within the ‘eBay auction services' category, there's more categories such as appraisal, listing services, packing and shipping, and shopping assistance.
I bet that either you can provide a service that falls under one of these categories, or you know of someone else whose services you could promote (and take a commission).
I would suggest that your first step is to browse these categories and see what people are offering. You'll soon see which topics are swamped with sellers thrashing each other on price, whereas others will have gaps in the market waiting to be filled by you.
Let's suppose that you have a friend that happens to be an expert at camera repair, yet in the local area his store has been struggling to find enough work.
A quick check in the ‘camera & photo' category of ‘restoration and repair' reveals just 6 listings, and only one seller seems to be a regular in that category, AND they are charging what seems to be a decent amount for the service. I would say that this represents a tremendous opportunity for someone else to come into that niche and provide a quality service.
That's just one example of how you can offer a service to a HUGE audience, easily and cheaply. I'm amazed that more sellers aren't doing this, services are such an untapped market right now on eBay.
Continuing with the camera repair example, imagine if the business owner produced some ‘camera repair' DVD training guides - simple instructions on easy maintenance tasks from an ‘insider expert', and then offered those DVD's for sale as a backend product.
They would sell loads of them, especially because the customer had recently experienced the pain of having a broken camera! It's the perfect tie-in product because the customer would no doubt want to do anything to prevent a reoccurrence, by means of preventative maintenance.
I love this business!