Hello,
The firmware of the 2600, 2800, 3400 and 5300 series now support Mac, web and 802.1x authentication. Mac adresses are checked against a radius server (MS IAS, Funk steel belted, Radiator, Free-radius, etc etc) and the authenticated client can dynamicly put in a vlan.
Mac authentication is not a strong security mechanism, its better to move up to 802.1x.
So using radius together with mac authentication you can easily automate your security.