There is the stackable <a href=”http://www.qlogic.com/Products/SAN_products_FCS_san5802V.aspx”>QLogic 5800V</a>.
I would recommend you look at either Brocade (highly recommended) or QLogic switches. You can see the ports counts you would need and can easily stack either product. I would recommend Brocade over QLogic due to have seen a hosted data center for Fortune 500 companies among others. Brocade appeared to be the highly used. Both solutions provide to great management tools to provide you visibility into your environment.
The question is, how many ports do you need today, and how many ports do you need to expand to?
Switches start anywhere from 8 ports, and can grow to 512 ports.
Brocade and Cisco are the vendors of choice for the larger switches. For smaller ones, you can go to Qlogic and others.
Do you have any inhouse expertise yet? That would play into your decision.