contacts

Did you follow the instruction on page 30 of the iPad User's Manual?

Info Pane (under the iPad when the iPad is connected to your computer)
The Info pane lets you configure the sync settings for your contacts, calendars, email
accounts, and web browser.
MobileMe

Â
You can use MobileMe to sync your email, calendars, contacts, and bookmarks
wirelessly with iPad. Click Learn More to create a MobileMe account, or get a
free trial.
Contacts

Â
You can sync contacts with applications such as Mac OS X Address Book, Yahoo!
Address Book, and Google Contacts on a Mac, or with Yahoo! Address Book,
Google Contacts, Windows Address Book (Microsoft Outlook Express), Windows
Vista Contacts, or Microsoft Outlook 2003 or 2007 on a PC. (On a Mac, you can sync
contacts with multiple applications. On a PC, you can sync contacts with only one
application at a time.)
If you sync with Yahoo! Address Book, you only need to click Configure to enter your
new login information when you change your Yahoo! ID or password after you’ve
set up syncing.

Thee are various boxes to chek in that pane.