I have a CSV item importer for MarketPress that I had developed by a third party.
It allows for uploading Item Codes, Sku's, Product variations, price, sale price, quantity, Images (using a url for embedding from a hosted image), Categories, product description, and tags.
If the category doesn't exist it will be created (the same goes for tags). I can't provide support for this plugin because I'm just an amateur when it comes to php. But if anyone would like to expand / build from this plugin please feel free. Or if WPMU DEV would like to incorporate it into the MarketPress build then they can and should. At any rate, it's a good start.
It was quite expensive, so donations are happily accepted here: http://hiltonglobal.org/csv-uploader/
The download is also located there.
Lately I've been getting an error when using it though:
"Warning: next() expects parameter 1 to be array, null given in /home/dippersh/public_html/wp-includes/plugin.php on line 407
Warning: current() expects parameter 1 to be array, null given in /home/dippersh/public_html/wp-includes/plugin.php on line 403"
Which will loop over and over again. Any help with this will be appreciated.
And once it messed up my site so much I had to reinstall the wp-admin folder. So if anyone wants to have a look at it and try to fix these issues would be great!