You should be able to see any of the calendars created under your Google account, as well as any you have access to (that you're sharing via Google Calendar).
To get them to show up in your phone, go to the Calendar app (not the widget), and hit the "Menu" soft key. The bottom-left option should be "Calendars". From there you can check and uncheck which calendars will show up.
If you've gone there and your new calendar isn't showing up, I'm not sure... it may be that your phone isn't in synch with your Google account, but I'll defer to people who know more than I do about such things.