I'm in no way connected with the guys at Selro but am amazed that they aren't better known (perhaps they're relatively new?).
Definitely worth checking out for multi-channel management of eBay, Amazon and web stores (Zen, Magento etc.) I'm just going through the setup process with the Selro system now, which is free for most things and ridiculously cheap for a few bolt-on features. Easily integrated with my Amazon, eBay and Google Base accounts.
Even their support has been good so far - I had a response in under an hour. My only niggle is that the website appears to be Flash based so won't be great on many mobile devices and a no-no for iPad. Perhaps an HTML5 version is in the works? Hardly a big problem though.