I remember attending a Drupal7 release party several months ago, 11 months ago actually. It was an exciting time, all this new stuff had gotten into core. I was hoping and looking forward to using the new functionality.
Create a contact form using webform module and webform conditional. Find out how to use different types of fields, setup recipients' emails and have dependent fields on the same page.
Here's a useful one you may not know about: field_get_items(). Basically, if you're trying to get field values off an entity, it can be fiddly - dealing with language, indices, etc. This function makes it much simpler.