All current powerbooks can be connected over an ethernet-wire. You should get a router at a cost of less than $40 and you can start right away. Actually you can even skip the router and directly plug the powerbook to your modem, but this solution is not elegant if you have more than one computer. If you want a wireless solution, you will need an access point which is mostly integrated in current routers. Not all powerbooks have an airport card built-in, but all of them are airport ready, which means you have the antenna and the slot for the airport card. Buying a powerbook with an airport card doesn't mean you won't be able to use pc access points or routers. All of them are at least 802.11b compatible which stands for wireless connection at 11mbit/sec. All current powerbooks also support airport extreme which goes up to 54mbit/sec. For these you will need 802.11g or 802.11a routers. As I said before, in these days these are all standard and pretty cheap. So no need to get an expensive airport extreme basestation.
powerbooks will get a major change when the G5 will be installed. However, this seems to be a tough task for apple and they announced, there won't be any G5 powerbook within this year. And I don't think we'll see any G4 update as well. So, it's a good time to get a powerbook, if you can't wait until next year.
