If you want to connect your PS3 directly with a Laptop use a CAT5e crossover cable with RJ45 plugs ( http://en.wikipedia.org/wiki/Ethernet_crossover_cable ) or a crossover adapter for normal CAT5e network cable. You need CAT5e or better for 1Gb/s connection or CAT5 for 100Mb/s.
You have to manually setup IP addresses for both PS3 and Laptop NIC within the same subnet.
Laptop: IP: 192.168.0.1, network mask: 255.255.255.0
PS3: IP: 192.168.0.2, network mask: 255.255.255.0
I think there is no good reason for doing that. Use standard CAT5e cables to connect your devices to your router. Your router will be DHCP server and sets up IP and network mask automatically. Also it will set the router IP as default gateway and DNS proxy so every device is able to communicate with the internet.