pfSense

Prevent ISC DHCP server from offering IP addresses to certain clients, typically a partial match of their MAC address. See discussion at http://forum.pfsense.org/index.php/topic,45596.0/all.html

One approach using ISC dhcpd would be to define class(es) and deny them in dhcpd.conf e.g.

subnet 192.168.100.0 netmask 255.255.255.0 {
    class "myphones" {
    match if (substring (hardware, 1, 3) = 00:19:66 );
    }
    pool {
        range 192.168.100.100 192.168.100.200;
        deny members of "myphones";
    }
    option routers 192.168.100.1;
    option domain-name-servers 192.168.100.1;
    default-lease-time 14400;
    max-lease-time 28800;

}