Can I use Macbook Pro as a wireless router? The only internet connection point in my current apartment is PPPoE service(via cable). I can plug it into my Macbook Pro to get internet connection. The problem is how to bring the internet connection to my iPad. Is it possible to configure my Macbook Pro as a wireless rounter for my iPad?

Or, if I have a separate wireless router with the PPPoE cable plugged in, how can I get it to work?
Try this...

Sharing your Internet connection - http://docs.info.apple.com/article.html?path=Mac/10.5/en/8156.html

Your mac will basically create a WiFi network for the iPad to join and then it will share traffic from the ethernet connector/PPPoE/cable.

Your mac's buit in help might be newer than the link I provided, so check there first. Also, be sure you turn off any firewalls if you don't know how or what holes to poke in them. You may be less secure, but it's a bit harder to set up the firewall on one interface and not the other.