Can I list on multiple eBay sites other than the one I am registered on?
How to list on multiple eBay sites
When creating a seller account, you are asked to register to a specific eBay site. This SellerID is now tied to the site you registered to. But you can still list on other eBay sites. For example, if you are an eBay US registered seller, you can still list on eBay UK. If you are using the API's, be sure to use the correct SiteID's, http://developer.ebay.com/devzone/XML/docs/Reference/ebay/AddFixedPriceItem.html#Request.Item.Site
If you are to use the SYI flow, you will need to login to the correct site. For example if you want to list on eBay UK, you need to use http://www.ebay.co.uk/.
If you use the API's, you also will need to retirieve all the information specific to each site you list on, shipping services, return policies, and etc. You can find this information via the GeteBayDetails API. You also will be responsible for different fees on each site,