Maybe old news for some of you, but HP has developed the Cisco switches for the HP Blade servers. The Cisco Catalyst Blade Switch 3120G and 3120X provide stacking functionality. This improves the functionality of the switches by creating a single switch from two physical switches.
Source: The Cisco Catalyst Blade Switch 3120 Series Switches are specifically designed to meet the rigors of the blade server based application infrastructure and provides HP BladeSystem customers with the ability to stack up to nine switches into a single virtual Switch.
The creation of a stack helps improving the availability and load-balancing of connections between the HP Blade environment and the physical network environment. More information about the new switches can be found here.