Mariusz Mizgier is correct, however you WILL find a lot of problems trying to get it to work, at least that is what happened to me and here are some information that could prove useful to you.

First, in order to be able to export/import we have to go to Settings->Configuration->General settings. check the box that corresponds to "Allow users to import data from CSV files"

click apply and then go to any products view and change the ordering to list, for some reason kanban and form do not have import/export as an option.

now you should see "import" right beside the create button, but let us leave that for later. you can now check the box for a product or multiple products and then the buttons "print, attachment, and more" will appear click on "more" and then export.

under export type it should be already be set on import compatible type but if it is not just set it correctly and then check "only export selection" now you just have to select the fields that you need to upload en masse. but make not of the ordering of fields because the names of the fields you are selecting WILL be different from the headers that will appear in your spreadsheet. and that can get quite confusing if you need a lot of fields. Also your first field will always be ID, be sure to leave that empty when you are importing so ERP will assign IDs to your items instead of using your items to overwrite your fields on existing items, it happened to me on my test platform :P

When you have all your products ready to import you can click on import of course, but when you choose your file to improt be sure to click "file format options" if the encoding is UTF-8 change it to latin1 so it can accept a wider variety of characters like the degree symbol and the like.

it is pretty simple once you get the hang of it.

I agree with Timo, you might need to import your products with a Python script. It is not a big deal, in the following post there is an example of importing products in a csv files via xml-rpc

http://erpmoldeo.wordpress.com/2011/05/10/importing-products-with-web-services-in-openerp/

hope this helps,

The easiest way to approach that is to create a single product on your own and export it with all fields, which are important to your company. After that you can populate this csv/xls file with real data and you are set to import it.