Hi Mike there are at least two options
1) The whole listing as templated could be copy/pasted from the HTML of the saved listing via the saved listing folder. At the right hand side of the entry for the listing you want to post somewhere else is the link labelled HTML. But that will include links to your ebay items in the SG and Auctiva store front. Including those on another site will probably get the listing pulled by them.
2) Open for 'Edit' the saved listing of interest and copy out the description text from the editor window you originally wrote the listing with and paste that in the listing for the new site.
3) My preference is always to create all listing text on my PC and save them at 'home' first. Originally I created the text with M$ Word but the HTML is bloated and can get interpreted differently on different sites, previewers and different browsers.
Now for expanding to other sites I write directly in HTML, you don't need to know that much but it can be a little tricky at times. I then paste the HTML into the appropriate space in the editor for the new site (assuming they have one !)
Plenty of free HTML editors available on the web.
From what I have seen of alternative sites in the UK most others are quite primitive compared to big-bucks greedbay so many other items such as p&p terms and conditions, shop front if any require many other tweaks so really only the basic description text and images appear to be portable.
However I still keep all my images hosted on Auctiva to at least simplify that aspect of multi-site selling.
I hope that helps, call again if I have missed or confused some point