CSVI Pro can do this for you but it's not free.

I'm not aware of any free extensions for importing products into VirtueMart.

I have used CSVI Pro previously and this works well.

One of my clients is using the Mass Update for Virtuemart to simplify product maintenance.

Searching the JED, I see there are other options but I can't vouch for any of these personally:

• HexData Import & Export for Virtuemart
• VM Products CSV

You can also check out other import options in the VirtueMart Extensions Directory.