"Stacking" in the HP E series (Procurve) world is purely a management stacking function allowing you to use a single IP address to access multiple switches in the stack for management only.
I assume you are thinking of stacking from a Cisco point of view whereby you have dedicated proprietary cables joining 2 or more switches together. Once the stack is created that allows you to treat it as a single big switch. On the Cisco this would then allow you to configure port 1 on switch 1 and port 1 on switch 2 as an etherchannel that would then connect to either another switch or to a server.
Unfortunately in the HP world that is not possible with the switches you have. You need to move to a Provision based unit (3500, 6200, 6600, 5400zl or 8212zl). With these switches you have an option called Distributed Trunking which would allow you to do what you want with LACP based trunks but only to servers (it doesn't work with connections to other switches). There are also other limitation to do with routing etc.
The other option in the HP world is the A-series gear (what come out of the aquisition of 3Com/H3C). These switches have a feature called IRF which is similar to the Cisco stacking but instead of using proprietary connections they use the standard 10GbE ports to link the "stacked" switches together. You can then create BAGGs (Bridge Aggregation Groups) that can span ports on different switches in the stack.
