Hello Sir,
I am a magento extension developer .I have developed many extensions some of them are very famous like multi seller Marketplace,Gift cards,ticket system,ebay connector etc ,but I work for a company thats why I cannot show them in my portfolio hope you can understand .
I have created ebay connector where have mapped categories ,shipping ,orders of magento to ebay.I can build this on for you .
If you want to hire me please come on chat so we can discuss it further.
Thanks