If those switches support it 802.1x port authentication is probably the best option you have.  You need a radius server to handle the authentication.  You have a few options there freeradius, Cisco ACS or NAC, Microsoft ISA or NAP/NPS.
Hello, I'm looking to implement some port authentication on my dell switches.  I have a few 3400's and 3500's series switches.  I was thinking about using MAC based ACL's but I don't know what the limitations are since I'm still in the planning phase. I also have IP phones to if that makes a difference. Are there other options I should look into? I'm basically wanting to do this to stop unknown computers from being plugged into my network.    I'd also like to be able to turn ports off if they are not in use, is this possible?
Network Security Options for port authentication