You can export VMs as OVF if you use VMware Workstation, if that's a possibility. If you're looking to do this with free tools, you can build the VM in VirtualBox and then export to OVA. However, I believe you'll then need to use VMware's Open Virtualization Format Tool to convert it to an OVF that's readable in vSphere.
That said, I'm not sure if I'm answering your question since it's unclear what type of product you're trying to turn into an appliance. If you have further details to share, it might get a more specific answer...